Well... considering a 650 TI struggles to run CURRENT games at medium/high... wait, 30 fps?
Yeah, you should probably be able to do that - there will be a few demanding games you won't be able to run that with, and DDR2 memory is probably going to hold you back a little, but that's okay.
That being said, that computer is seriously going to start showing its age soon, especially with the older, much slower memory.
Could you link benchmarks between DDR2 memory and DDR3? I'm more concerned about the CPU than the RAM.