Hey I got no money, in this economy, as everyone else, so what the best 'bang for the buck' deal'?

I figure multi-core cpu , 8 gb ram for starters...
Going to keep repeating the question until you get an answer that you like? (Insert expletive here.)
I have to modify my original response. The CPU compatibility list for the M2N-SLI includes AM3 CPUs. It's limited to 95W processors, so you could use an Athlon II X4 640 or a Phenom II X4 945 (but not a 955 or 965).
ASUS - Motherboards- ASUS M2N-SLI
Some are actually for sale, new:
Newegg.com - Computer Hardware, CPUs / Processors, Processors - Desktops, 65W, 35W, 45W, 55W, 95W, 73W, Socket AM3, 77W, 69W
The Phenom II X4 645 is available at Amazon, but only used, at over $100.
8GB of DDR2 isn't going to be cheap.
You could buy an AM3+ motherboard, a quad core AMD FX CPU, and 8GB of DDR3 memory for less than $200 new. (If your Windows license is OEM, you'd have to buy it again with a new motherboard.)
Putting any significant upgrade money into such an old system would be foolish. Don't do it. Replace the CPU fan on the old processor. The old system isn't bad. Save your money while you're researching the new system that would make the most sense for you.