My current rig is:

Athlon 64 3500
1GB PC3200 RAM
nVidia 7900 GT

I may get one computer upgrade as a present to myself for Christmas, and I'm trying to think about what it should be. I know Core 2 Duo stomps the shit out of the Athlons right now, but is the performance difference worth the cost of buying a new processor, motherboard, and RAM?

If it's not, I may just get a dual core X2 processor, and maybe get some more RAM. I won't touch the videocard until Direct X 10 is fully established and cards supporting it are readily available and tested.

So, what say you 404?

Well, 939 is dead technology, so any money you spend on upgrading your rig is money that won't help you with a better system down the road. If you have the money to upgrade to AM2/LGA775, I'd do it since it will save you in the long run. Upgrading a 939 setup is essentially a stop-gap to buy yourself about 18 months' time before having to make a serious investment in order to stay with the curve. If you want to hold off on major purchases until DX10 is stable and fully supported, it's not a bad option. But the 775/C2D/DDR2 setup is worth the price compared to an AM2/X2-FX/DDR2 setup, and it's a no-brainer compared to the 939/64/DDR setup you have now.

Plus, 939 chips aren't any cheaper compared to their AM2 counterparts. (In fact, some, like the X2 3800, are more expensive on the old socket.) So you're really not saving any money by sticking with old components, you're just keeping yourself from having to buy too many new parts at once.

That is true, there pretty much isn't anwhere to upgrade to. And I really need some new RAM anyway, because I think this RAM is corrupted or something, because everytime I run a game, it will eventually crash, and my computer isn't overheating or anything.

The only really painful thing will be buying a new mobo since I have no problems with this one...

I think I may go to Core 2 Duo then. I'm gonna wait awhile until Direct X 10 is established (will probably get Vista from my college's MSDN program) and then do a massive overhaul, and then either sell my current stuff or give it to my mom (she's still running an Athlon XP 2500)

I'd wait for a bit to get new ram. DDR2 production is going up and will bring these grossly inflated prices back down. Look for price drops in December or early 2007. They should go down again in April from what I've heard.

Anyways, if you've got the money, go for C2D in around a month. A 4800+ will set you back $300 or so. An E6600, on the other hand, is around the same price, but with better performance.