Older motherboard -> Newer video card

Hello all - I'm hoping somebody can answer a question I have. My last build was about 2 years go. I purchased the Gigabyte motherboard GA-EP35C-DS3R with an E8400 and kept using my existing GTS8800.

I'm at the point where I would like to start fresh and move to a new i7 system but that simply isn't in the budget, at least not for a while. However, if possible, I could update the memory and GPU.

My question is, I know my current board isn't PCI-X 2.0. Will more modern GPU's (Radeon 5850/5870) work in my PCI-X 16 slot even though its 1.0? If it does work, do you think I would notice a significant performance hit? I currently have DDR2 memory but my board support DDR3.

It would be great if I could simply update the RAM, GPU, Add a SSD for the OS, and upgrade to some Raptors. That would save considerable cash and give me the performance increase I'm looking for...I think.

Thanks in Advance,

Merloin