Ok, the question is how deep do you want to dig
DFI offers the most challanging OC MBs.
THe DR-SLI is an excelent piece, the "Expert" on the other hand is even more challanging and currently has an unpublished issue and best to avoid untill they get the BIOS quirk ironed out.
Asus has a new SLI that is very good to but hard to find.
If you want serious graphics the 7800GT -7800GTX is the answer. For now 1 will game awesom and you can add a second later.
On the RAM... 2x1G is the way to go... at least DDR500 or if you can find the Geil One get it ... you will see it with CAS1.5 specs.
On the PS... an Sli certified unit is a MUST.
There are serveral great PSs out there too!
OCZ, PC Power, Silverstones Zeus, Sunbeam NUUO 550 very reasonable price very dependable unit if you can find one and there are other very good ones too!
The Zeus is very highly recommended.
On the CPU... the Optron 148 have a new core stepping of CACJE 0546 which I've found very little on but had OCed to 2900 Verified... the CACJE 0548 is out there but as of yet I've found nothing but will be working an OC on one for a friend. So, unless you fine the older CABNE, CABYE in the 0540 or older dates it's unclear what you will get, they typpically hit 2800-3000. The CAB2E which some discount has also seen 2900. verified ... It's the GABGE that seems to be a bit of a dog!