Comments/Advice on Upgrade thoughts/plan

Ok here are the current specs and my thoughts afterward. Wanted to build an all new quad based one, but money got a little tight and can't afford a whole new one anymore.

CPU: AMD Athlon 64 X2 5600+ 2.8 GHz AM2
GPU: Sapphire HD 3850 256MB 256-bit GDDR3
RAM: Corsair XMS2 2GB (2x1) DDR2 800 PC2 6400
HD: WD Raptor 150 GB
MB: ASUS M2R32-MVP AM2 580X
PSU: Silverstone 600W

I think the HD, MB, and PSU should be fine at least for now.
I also believe that the CPU should be able to hold me for a while longer.

RAM I could upgrade but not sure if it would be worth it to got to 4GB as not all would be used as I'm on XP 32, and also not sure if it would help in gaming as most recommended specs I see are still at 2GB. Would like to hear some thoughts on this? Go for another 2x1, just buy a 2x2, or just keep the 2GB?

GPU I think is the biggest thing that if I upgrade could prolong my PC and help it be able to power some of the newer games coming out. My MB only has a 1.0 16x so I hear 2.0 is backward compatible so I'd go for that since I heard they may also be some problems with the 2.1 back to 1.0. So I was thinking that going for a 1GB 5750 or 5770 could be a big help and I think my PC should be able to handle it and help prolong it. Might be able to swing a 5830 but not sure I think a 5770 should be able to handle things for a while. Thoughts on choices?

Any different or additional thoughts please throw your input in. Thanks.