Thanks for the information
I went for an XFX 9800GT with 512MB DDR3 memory, should be here tomorrow. There isn't realy any point in me getting a faster card as my system isn't powerful enough to make use of it. My system specs:
Intel core 2 with both cores @ 1.8Ghz each
4GB of DDR2 ram
No idea what the bus speeds are, not blisteringly fast by todays standards tho.