Will the MacBook Pro (15-inch Glossy) (Model # MA601LL) be enough for me?

Hello all,

I am new to this forum and to Macs in general and I have some questions regarding a refurbished MacBook Pro that I am interested in purchasing and whether or not it will be sufficient for my needs.

First, here is the link for the specs on the MBP in question:

http://support.apple.com/kb/SP32?locale=en_US.

It's a few generations old...

In addition to the stock specs, it has been upgraded with the following:

2x1GB (SODIMM) 667MHz DDR2 SDRAM (otherwise known as PC2-5300)
and
a 200GB, 5400RPM SATA hardrive.

I want to be able to use Logic Pro for both at-home composition/production and live performance. What I'd really like to know is the following:

1) How many software synth plugins will I be able to run at the same time? I realize that they vary in size/strain on resources, but on average, what can I expect?

2) Will this setup be stable and usable in a live performance setting, using Mainstage, and switching quickly between programs which may have different plugins that need to be called up?

3) Would an external audio interface be necessary if I am not recording audio?

4) I am planning to use my current 88key M-Audio controller keyboard via USB to the MBP. Are there any issues with latency if I use this setup?

Any insight would be much appreciated!

Thanks.