Ill agree the 6600 and upwards are better. But the 6200 will work. And its a good cheap option.
And not all 6200's are 64bit memory bus.
http://www.giga-byte.com/VGA/Product...V-N62128DP.htm
Its not GT, but its a 128bit bus and quite affordable. (only 128mb DDR on it) but im sure there is a 256mb one.