|I made my recommendation & kuwese seconded it. I based the selection on what would work with your 300W power supply.|
The memory used on the video card has nothing to do with the memory used by the motherboard. GDDR2 memory is slow, that's why video cards with GDDR2 are generally cheaper than cards with GDDR3. Stay away from cards with GDDR2 memory.
You also have to look at the memory buswidth. Do NOT get a 64-bit card for gaming...go with 128-bit or better. And as for PCIe 1.0 vs PCIe 2.0, there's built-in backwards compatibility so either will work.
Just get a Radeon HD4670 & everything should be fine. And like I said in my other response, get some more RAM...1GB isn't enough anymore. It's the minimum requirement for Win 7. You need at least twice that much for decent gaming. Most are running 4GB (or more) these days.