I love buying older parts and then maxing them out...
I'll list what I would do, you can choose what to upgrade.
1. I'd find out if the mobo is AM2 or AM2+ and if it supports 125W CPUs. If it does I'd pick up a Phenom II X4 965. they are like 90 bucks and very good bang for the buck. I'd also invest in a aftermarket CPU cooler if getting a new CPU and overclock to 4Ghz.
2. I'd see how many RAM slots I have. 4GB is ok actually but if you have 2 free slots, you can grab another 4 GB no problem. It's not easy finding 4GB DDR2 RAM in a single stick (for a good price). If you're upgrading the RAM, try to get the same speed as the one you currently have.
3. SSD as a boot drive and a fresh install of windows is a must. No questions about it.
4. If you keep your system as is I'd pick up a Radeon 7770 or 7850 1 GB. Anything higher and you will bottleneck the card with your computer. If you upgrade to Phenom 965, 8 GB of RAM, you can get a 7870, GTX 660 etc...







