Welcome Back
For Gaming stay away from the mac unless you dual boot into Windows as most games are not ported across to mac.
Grab yourself a Core2Duo CPS along with a large HDD and 2GB of RAM and you should be setup for a while.
Get the PCI-E cards with a compatible motherboard and again you should be right. If you want future proofing make sure your motherbord can support the cards running in SLI.
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