How to upgrade my Rig

I am getting ready to 5 box for a while. First thing is to upgrade my gaming rig to something that would handle 5 wow instances at a decent framerate (possibly I would like to have a bit more power than what I need, so that I'll be fine with any resource requirement increase we will see in the next months, if any).

At the moment I have a 24w" monitor and an old 17" one (which I am currently not using). My GPU is an HD2600 (pretty good for one instance, probably even two or three on low fr, but not high end).

I am a bit limited on the space, so I can't get another bit monitor, best I can do (to have two monitors) is the 24" and the 17" side by side.
The plan was to use the 17" for my main, and the 24" for the 4 slaves (so that the windows are not so small).

That's a dual monitor, and with different resolutions. Is it going to work?

I was planning on buying a GTX280 card, and attach the 24" monitor to the GTX and the 17" to the HD2600. However I found a topic here saying that only the main adapter will be used. Also, looks like Vista won't like using different video drivers at once, is that true?

Given my space limitation (maybe I can fit something bigger, but definitively not 2 24" monitors) what would be the optimal upgrade strategy for me?


On a slightly different topic.. I am planning on going 8 GB as that looks enough. Should I get 2 4GB banks instead of 4 2GB (which are cheaper) just to have the road for future upgrades or it is not worth it?


PS: sorry for my English.