Gaming Computer Under $900?

go with a p45 chipset mobo. If this means dropping your cpu to the e7xxx range it's ok. You'll have more OC ability. You will also leave open an upgrade path with the option to crossfire your 4870's, (with a psu upgrade) make sure to buy one with dual pci-e 16. socket 775 cpus are not going away anytime soon, so leaving the option and upgrade path is a good idea, you will always be able to dump a quad in later, and i'd find it hard to belive that an oc'ed q9650 will be underpowered in 2-3 years, though they will most likley be much cheaper.