Pretty nice setup you got there!
I use DiabloMiner for Windows... There are many other GPU miners out there, and you can find a list of them on the wiki:https://en.bitcoin.it/wiki/Category:Miners
The one I have is run by Java, so you would have to install JRE too, Oh and also the Ati SDK 2.1
After thats done, join a pool or just mine with the 20 comps together.
I'm myself in a pool, but thats just because i only have 2 computers. I mine for http://bitcoins.lc
You might want to check it out too
Steady payments etc.
The problem when mining solo, is that you get 50BTC, at once, when a complete block is done. At a pool, you can get steady payments to whatever address you want!
Oh and what more.. hmm, PM for more info