I need help with something... Gaming related

I own and PS3, and a PC that I have built myself, and I was wondering if you guys could help me decide on something.

A - Additional Graphics Card + New PC case
B - New (faster) Processor + New PC Case
C - New TV that supports 1080p for gaming
D - Mix of above; specify?

I am limited by funds £250 - £300 being the maximum.

For 300 you should be able to get a HDTV , though likely not huge, and a decent graphics card. **** PC Cases.