|The Athlon64 X2 is MUCH better/faster than the older/slower Athlon XP. They are NOT interchangeable in the same motherboard though. The Athlon XP is strictly a socket A CPU, the Athlon64 X2 comes in several socket "flavors" - 939, AM2, AM2+.|
As kuwese stated, the 9500GT is not a good gaming card. If you haven't gotten it yet, I strongly suggest you get something better.