If you already have one 6800GT it might be worth snagging a second one for SLI... Newegg has an Asus for $239 in stock that would work, but if your building a new PCI-e rig now & are ready to spend $400 +/- on a GPU I'd go with a single 7800GTX instead... it'll be faster then 6800GT's in SLI, cost a bit less & use less power.