Oh, then just go for a good 890 chipset AM3 mobo with 4 gigs of DDR3 and a phenom II x4 955.
A samsung spinpoint F3 would be good for a hard drive. I'd hold off on SSD's for the moment. The 28nm process is supposed to be rolling out soonesque and will make them cheaper.
Then you might as well get win7 as well.
If I were you I'd go ahead and sell the parts you'd replace on ebay, just put the mobo/CPU together - that seems to go higher that way.
You should get the performance you want doing this and come in way under budget.
What's the PSU you're using?