Most efficient upgrade?

[megaerik00]

I built a budget pc for my wife a few years back and its about time to get upgrade it a bit. She bought a new game (Champions Online) and her rig is pretty choppy on the lowest settings.
Here is what we're working with:

CPU Newegg.com - AMD Athlon 64 X2 4800+ Brisbane 2.5GHz 2 x 512KB L2 Cache Socket AM2 65W Dual-Core Processor - Processors - Desktops
MOBO Newegg.com - MSI K9VGM-V AM2 VIA K8M890 Micro ATX AMD Motherboard - AMD Motherboards
RAM 1gig of Newegg.com - SUPER TALENT 1GB 240-Pin DDR2 SDRAM DDR2 667 (PC2 5300) Desktop Memory Model T6UB1GC5 - Desktop Memory
GPU replaced a fried 7300 gt with a bfg geforce 8400 gs 512 mb

I know there is a lot of room for improvement, but i just need the most cost efficient upgrades to get rid of the choppiness on mid settings. I know i need to upgrade the ram, potentially the gpu and cpu, what do you guys think?

In case it helps, the recommended system for champions says intel E8400 core2duo, 2gig ram, geforce 8800.

 

[Muffin Man]

possible upgrades depend on how much money you have to upgrade, so whats your budget?

 

[brozium]

CPU is ok.
Get 2gb of RAM DDR2 800.
Based on Tom's Hardware, the best bang for the buck is a 9600gt.

Go here, Antec Power Supply Calculator to check if you need a PSU update.

 

[megaerik00]

I have the money, but the more frugal i can be the better. I suppose i could justify spending up to $200, but if i can get it good enough for $100 id be great with that.

 

[Fat.Clown]

another stick of ram and a HD 4670 and you should be good to go