I own the full WIVI collection and whilst the brasses are excellent, the woodwinds aren't great...they sound thin and fake to me, especially the clarinets and oboes. Also, you really need the WIVI Professional Edition Player to get the most out of WIVI and that's $379 on its own without any sounds. (The Pro player enables you to access a zillion different parameters in order to customise every single nuance of an instrument's sound and response....it's invaluable) However, even the Pro player - in my opinion - can't save most of the WIVI woodwinds in terms of realism. I use WIVI all the time for its brasses but use SampleModeling for winds. It probably doesn't help that I'm a professional sax player and am particularly sensitive to woodwind emulations but I think the SampleModeling clarinet and oboe products absolutely nailed it. The saxes are pretty good, too, but nobody has really nailed saxophone emulations yet, probably because there are so many variations in saxophone sound and style that it's incredibly difficult to please everyone with a single product. There are 2 different SampleModeling products for saxophones - SWAM and Kontakt-based - and the difference between the two really comes down to playability on wind controller. The Kontakt-based saxes probably have a slight edge in terms of sound realism but the SWAM saxes are more expressive and responsive with wind controllers. However, the WIVI package is comparatively much cheaper when you factor in how many instruments you get, compared with the single-instrument SampleModeling products. It all depends on how realistic you want the sounds to be, and how much money you want to spend. WIVI woodwinds will be fine for a hobbyist but if you want to play in a pit orchestra or with other live instrumentalists - or just have high expectations - you'd be best to use WIVI for brasses and SampleModeling for winds. SampleModeling's brasses are also very good but WIVI is comparatively much cheaper with its multiple instruments and very good sound/playability.
I'm not quite sure what you mean by the "power adaptor that came with VL70m". Do you mean the WX cable that plugs into the front of the VL70m and powers the WX5, in addition to transmitting MIDI data to the VL70m? Or the VL70m's AC power supply? If you're talking about the AC power supply, I'm almost certain that it will also power the WX5 if you're ok to ditch the VL70m....pls clarify and I can check for you. I know that the WX5 requires 12V DC with a centre-positive tip and am almost certain that the VL70m does, too, because Yamaha tends to build the same power requirements into most of its electronic music devices.
If you're wanting to use the WX5 to control softsynths, you're going to need to somehow connect the WX5 to your computer. You CAN do this by connecting the VL70m MIDI Out to a MIDI interface that's then connected to your computer, but I personally prefer just using rechargeable batteries in my WX5 and connecting the WX5 directly to my MIDI interface using a MIDI cable. Eneloop Pro rechargeable batteries (the black ones) give me at least 10 hours playing time on my WX5, and probably closer to 13 hours...but I always charge the batteries before they die on me and so I've never measured the full playing life of a set of rechargeables. Actually, I normally use a MIDIJet Pro wireless system and don't use cables at all but the goal is the same i.e. connecting the WX5 to your computer using a MIDI interface and ditching the VL70m altogether. I also had a friend make me a 30ft cable (using Cat 5 cable) many years ago that supplies power to the WX5 AND carried MIDI data, too (but I never use it anymore because I now use a wireless MIDI system). Each end has 2 connectors: the sound module end has a female socket to connect the external AC/DC power supply and a 5-pin MIDI plug for MIDI input to the module, and the WX5 end has a male DC socket to power the WX5 and a 5-pin MIDI plug to connect to the WX5 MIDI output.
However, if you still want to use the VL70m sounds IN ADDITION TO softsynths like SampleModeling or WIVI, then I'd simply connect a MIDI interface to the VL70m's MIDI Out and then connect the interface to your computer so that you have the best of both worlds i.e. VL70m sounds AND MainStage softsynths. However, if you do this, I recommend setting up some "silent" patches on the VL70m when you use the softsynth sounds so that the VL70m isn't sounding at the same time as the softsynths. For example, you can configure MainStage to send patch change commands to your VL70m if it's connected to your computer via a MIDI interface. If you want to play a softsynth, MainStage can switch to the "silent" patch on your VL70m so that no sound is heard from the VL70m BUT your softsynth sound in MainStage is being heard instead. Or, if you have an audio interface, you can also run the audio from the VL70m into your computer and MainStage and simply silence the VL70m audio channel when a softsynth is being played. This way, MainStage is your central "command hub" and you don't have to the touch the VL70m at all during a performance. I did that for a few years with a VL70m and Roland XV5050 and XV2020 modules until getting rid of hardware synths altogether about 8 years ago. There are lots of ways to accomplish virtually whatever you want by using MainStage and a good quality audio/MIDI interface. (I should clarify that a MIDI interface and audio/MIDI interface are two different devices. The former handles MIDI data only, whereas the latter handles both audio and MIDI.) Just bear in mind that if you want to use the VL70m AND softsynths from your Mac, you'll need to connect the audio outputs from BOTH devices into your amplifier i.e. VL70 audio output and Mac audio output. An audio interface (or a small audio mixer) will help to consolidate these into a single output if that is what you'd prefer to do.
Something that's really important to know: do you plan on using the audio out from your Mac, or are you planning to get an audio interface (with integrated MIDI in/out) to use with your Mac? The reason I ask is because whilst a basic setup using the Mac's audio out is a simple and cheap first step, I'd recommend that you get a good quality (i.e. not cheap crap) audio/MIDI interface if you want to take things to a whole new level of flexibility. A good quality audio interface will usually also have excellent software drivers with lower latency than the Mac's built-in audio, too. But be aware that a good quality audio/MIDI interface will start around the $400-$500 mark....and going cheap on this aspect is a sure-fire way to encounter problems. You'd be best to do it right the first time and buy a quality product rather than end up having to ditch the first crappy device and still have to buy a good one anyway. In any case, can you let me know if you're just wanting a simple, cheap setup to start with? Or do you want to take things to the next level? 😉
Sorry for the long post...there are just so many possibilities with MainStage and softsynths, and even more if you want to combine these with a hardware module like the VL70m.