First, if you possibly can - wait until next month to buy processor. Intel is supposed to have a price cut coming sometime in April.
I have two computers with Core 2 Duo processors:
XP Pro, Intel D975XBX2 (Bad Axe 2), BFG 7800GTX 256MB,
2 X 1GB Crucial Ballistix PC2-8000 DDR2 1000MHz, Core 2 Duo E6700 2.66GHz CPU @ 3.6 GHz, Zalman CNPS 9700 NT CPU cooler, 2 X 150GB Raptors in Raid 0 on the Intel Matrix controller - the board also has a Marvel controller (8 SATA ports), one Seagate 320 GB 7200.10 "Perpendicular recording technology" hard drive for back up and extra storage, LITE-ON 20X DVD, and Sound Blaster X-Fi XtremeMusic sound card.
This is the computer I use for everything. I'm not much of a gamer - I have Combat Flight Simulator 2, Flight Simulator 2004, and Flight Simulator X - so I don't know for a fact that it will meet your needs for gaming, but I think it will. I built this computer back in November and it has been running 24/7 with the CPU overclocked to 3.6GHz since then (I run World Community Grid -
http://www.worldcommunitygrid.org/ ). I am very happy with it.
The only problem I've had has been with FSX and that's the game, not the computer. I also tried FSX on a computer with a P4 670 oc'd to 4 GHz with a 7800 GTX video card and 2 GB RAM and that wasn't enough computer for FSX either. Either of those computers run CFS2 and FS9 just fine with all the setting cranked up and @ 1600 X 1200 (Dell 2001FP).
My other Core 2 Duo computer:
Vista Ultimate, Intel DG965WH, 2 X 1GB DDR2 667MHz, Core 2 Duo E6600 2.40GHz CPU, Zalman CNPS 9500 AT CPU cooler, Seagate 320 GB 7200.10 "Perpendicular recording technology" hard drive, and LITE-ON 16X SATA DVD. I'm using the onboard video and sound for now. Not much to say about this computer........ I got it running at the end of January when Newegg started selling the OEM version of Vista Ultimate. The motherboard does not have any overclocking option in the BIOS so it's running at stock speed. About all I've done with it so far is play around with Vista a little (I'm
not impressed with Vista) and run World Community Grid. Haven't had any trouble with the computer though..... (If I were building this computer again I'd buy another Bad Axe 2 instead on the 965 board so I could overclock.)
Neither of those boards are SLI compatible. The DG965WH has only one PCI Express slot. The Bad Axe 2 has two PCI Express slots and is CrossFire compatible. I've heard of people running SLI on the Bad Axe 2 with hacked drivers but I've never tried it. One video card is enough for my purposes.