But, I HATE Windows and I know how to do windows games on a mac.
You hate Windows, yet you're a hardcore gamer? Inevitably, you'll be booting into Windows for 99% of the games out there. Buying a Mac Pro for "hardcore gaming" accomplishes the following:
1. More money spent than necessary because you bought workstation-class hardware that makes absolutely NO difference in games.
2. Limitations on GPUs that actually boot into Mac OS. Additionally, you're limited to two PCIe power connectors on the logic board (unless you mod with splitters and/or a secondary PSU) and one of those are already used by the stock 5770 card; both of them if you order with the 5870.
3. No official SLI support on the logic board (if you're an NVIDIA guy); but ATI Crossfire has been known to work.
4. No analog mic input, forcing you to use a USB sound card or a dedicated sound card (that only works in Windows, of course) if you plan on using a headset.
There's probably more points I'm not even thinking of right now. But the main point here is that from a gaming perspective, spending that much money, given the platform drawbacks is completely insane, IMHO.
Look at this way: $2500 buys you an ENTRY-LEVEL Mac Pro with only 3 gigs of RAM and a so-so graphics card. That same $2500 can buy you one beast of a gaming rig. Is booting into Mac OS for those rare occasions you WON'T be using the machine for gaming really worth that hassle?