The Gen3 has been the pick of the bunch.. at least in my experience.. They are the most reliable albeit the harddisk in the 1TB model was a samsung which wasn't the greatest.
I'm getting drop outs of connection, I'm wondering wether to get a new TC as this is getting old and probably EOL anyway.
Do you notice poor wireless or dropouts on your phones or appleTV? Or is it just the Mac.
The fact is.. you need to figure out where the issue is.. Yosemite, as the worst update we have had so far from network point of view can have loads of dropout issues.. and you will know the difference because the phones etc are fine.
It can also be caused by interference since wireless is now used more and more and the neighbours might have bought high power equipment that is simply swamping your unit. You need to do a wireless survey using some software.. eg the built in wireless diagnostics in the Mac will work. But you need something to use on a phone or ipad if you want to measure it around the house.
Not all NAS support Time Machine.. and if the issue is with the TC you will still have the same issue using NAS plugged into it.. unless you use ethernet.
If your only Mac is the iMac then for backups buy a USB external drive. (FW800 is better for older Mac but any new one the USB3 is faster and cheaper) will be better and much more reliable.. TM in Yosemite is poor.. but works better to local drive than network.. which means both the TC and a NAS are going to have issues.
You can use a different backup software if the problem ends up TM .. CCC (carbon copy cloner) is excellent 3rd party as is Chronosync from what I hear.. but I actually use CCC.
It is still worthwhile having a local backup.. CCC can do a bootable clone which is the best way to get a computer running again. And the easiest way to recover a file.. although TM is better for history.. and to pickup older versions.
So do you buy a new TC??.. I have kind of fudged around answering.. I cannot give you a categorical answer.. Yes it will solve your problems.. I am not at all sure it will.. No .. because you don't need it with cloud and other possibles.. but I would say.. don't just assume the current TC is the problem.. if you then buy a new one and discover the problem doesn't go away you are back in the soup.
