Bushape
I bought a new computer the 1st of May. It had a 9100 in it and I upgraded to a NVidia 250 GTS which is a single slot, double sized video card (I only had one slot) so that worked fine and you can get them for $150 or less and it plays Black Ops just fine.
738 Mhz Core Clock, 128 processor core, 1782 MHz Processor Clock, 1024 mb. I get about 95 fps. I am no computer geek, so I really don't know what all of that means. But I know it works. It runs my windows 7, 64 bit just fine.
There is always something bigger and better.
Go with whatever you can afford. But remember in 3 months a bigger, better one will be cheaper. I hate that.
Good luck
FPS in computer geek world means "frames per second" 90 for Bo is alright .. seems like i cant go as high as i can with Cod 4 its prolly they run this game on lower frame rate. but u can try with your card .. open up console and type in "cl_drawfps 1"(i cant rememebr by heart) it will show your FPS rate on the top right corner of your screen and then type "com_maxfps 150" see what how that works for you