Which part of my system to upgrade first? GPU or CPU/Mobo/ram/OS?

[LW07]

Alright, i've been planning to upgrade my rig for a while now and i want to know which i should go for first, a video card upgrade or CPU/Mobo/ram/OS upgrade.

The first one i'd upgrade in around november/december and the other upgrade i would perform in March. Doing it to spread the costs of upgrade.

My current system specs:
S939 Athlon 64 x2 4800+ @ 2.4ghz(stock)
2 gigs of PC2700 ram
X1900XT 512mb @ stock speeds
PC Power and Cooling 510-SLI
Soundblaster Live! 24-bit card
Windows XP Home Edition
400GB SATA II 7200.9 Seagate drive

Planned components in upgrade:
Windows Vista 64-bit Home Premium
Q6600 or E8500
Radeon HD 4870
4 gigs of DDR2 800 ram
Might get the WD 640GB hard drive, i hear its almost as fast as a raptor
$75 gigabyte Mobo

I primarily do games, but i'd like to get good performance for the next two years so i'm leaning toward the Q6600.

 

[Denithor]

GPU has a much greater impact on gaming than CPU, that would be the first thing to upgrade. You may find that you don't really need a CPU upgrade just yet if you get the right video card.

What resolution do you use for gaming? If 1920x1200 or higher go for the 4870 1GB. If lower resolution go for either a GTX 260 or the 512MB 4870 (these two can be had off eBay for <$200 with MS cashback).

 

[Roguestar]

Denithor is completely right. As per your resolution, choose the 4850 or the 4870-1GB.

 

[LW07]

My current monitor's max resolution is 1440x900.

I guess i'll just get a 4850 and keep on trucking with my X2 4800+, upping the GPU all the while as needed, until dual-cores are obsolete...