It would help if you told us what PC you have at the moment?
You have a 9600pro, and a 350 Watt power supply but what else?
It may be that your best bet is to get a decent graphics card now, and upgrade the rest later. So this 256MB 8800GT from Scan would be the way to go .
Computer hardware and software at amazing prices, available online from Scan Computers UK
Could also look at the 3850 and 3870 ATI cards, but at the moment they are more expensive and slower than the 8800GT (256Mb)
But if the guts of your PC are too slow, then maybe you should get a decent quality core system now, and hold off on the graphics card until later.
For £180 I'm afraid you cannot get a decent gaming system - especially if your target is crysis