Get DDR-RAM. Don't get more SD-RAM. DDR-RAM makes the world of a difference. Get at least 512MB of PC3200 DDR-RAM. I would recommend maybe 768MB if you are into games like Far Cry. I am getting another 256MB because of some stuttering issues.
For cost effectiveness, you are going to want to change that processor to a cost effective Barton 2500+ that's very overclockable.
For performance, you might want to go with the AMD Athlon 64 3000+
For the motherboard, for cost effectiveness you want to get the Asus A7N8X (for Barton).
For the motherboard, for performance you want to get the Asus K8N-E Deluxe (AMD 64).. the K8N-E deluxe is based on the NForce 3 chipset and is better then the K8T800. This board is a tad bit more expensive then others but is very effective.
As far as the video card goes, the cost effective but performance packed solution is the Gainward FX Powerpack FX5700. It sells for $99: Here
The FX5900 XT for $193: http://www.allstarshop.com/shop/prod...HKHM9UDVLKART6
There is also the Fx 6800, but it is far more expensive. I did hear about a cost effective Fx 6600 that is a scaled back model but am not sure where it sells.
Edit: Furgy, consider this my apology for being mean to you earlier.