AMD 761 DDR chipset based mobo, athlon 1.4, 256 or 512 meg PC2100 DDR SDRAM. ABIT will soon release a brand new mobo supporting DDR memory that also includes the highpoint RAID controller. If you have an extra $150, buy a second identical hard drive and set up a RAID 0 array. I did this using 2 30gig IBM deskstar 7200 rpm drives ($135 each 3 months ago) and it's fast as sh*t (on ABIT's SA6R mobo).
If you can wait a week or two, wait for that new mobo and see if it stacks up in the hardware reviews. If it does, that would likely be my choice for a new gaming system. Oh yea, a GF3 would be nice if you have a lot of money, but if you want to save a few hundred bucks and get 90% of the speed get a high end GF2 or even a Voodoo5-5500 from the bargain bin. Otherwise, visit
www.anandtech.com and take a look at the motherboard roundup they posted up a few days ago. They have a few recommendations of course.
Hope this helps.