Never heard of an X9550.
Do you mean an X1950?, if you mean an Radeon 9550, then nope, the X550 is much newer and better, but if you mean the X1950XT, then yea its good performance, but i would reccommend waiting to see what new from ATi/Nvidia, the R600 is coming soon, think the end of this month, and then Nvidia are releasing mid range DX10 cards (8600GTS) which should be cheap at around £100-£150, so best bet is to wait.