I have an Asus A8N32-SLI Deluxe S939 motherboard with an Opteron 185 which does 3.0GHz all day long. I also have 4GB of DDR400 Cas2 memory in the board which runs at DDR600 all day long. I've been offered $400 for the complete setup, but I'd just rather keep it. I think I paid $300 for the Opteron in 2006, the motherboard was around $100 and the memory was around $150, also in 2006. I might upgrade next year in 2010 but there will have to be something special gaming wise to make me want to do it.
I agree with nemesismk2, this machine (with the right video card) plays any game I want it to at 1680x1050 on full or near full setting. I mostly play BF2 these days and I can easily max all the setting with 6X AA and get well over 100 fps. Upgrade? Why?
Honestly, I don't care of about synthetic benchmarks or any of that nonsense. With my WD Rator 10k HD the system is fast and when I have used faster, C2D and C2Q desktops I haven't noticed a speed difference in Windows related tasks. Games, sure, maybe I'll get 150 fps instead of 120 in CSS. Don't care.