Advice on choosing a card, mainly 260-280?

I am almost done with my build, only the GPU left. I want to play mostly newer games Fallout 3, Bioshock, Wow, Farcry 2 etc. (not crysis) on good settings on a 21.5" screen.

My question is should I go with a 275 or a 260 or what? I don't really want to Sli or crossfire.

Here are some cards I was thinking about:


BFG 260
[url=http://www.newegg.com/Product/Product.aspx?Item=N82E16814143140][/url]

BFG 275
[url=http://www.newegg.com/Product/Product.aspx?Item=N82E16814143183][/url]

EVGA 280
[url=http://www.newegg.com/Product/Product.aspx?Item=N82E16814130493][/url]




Here is my build.

Mobo:

GIGABYTE GA-MA770T-UD3P AM3 AMD 770 ATX AMD Motherboard - Retail
[url=http://www.newegg.com/Product/Product.aspx?Item=N82E16813128392][/url]

CPU:

AMD Phenom II X4 945 Deneb 3.0GHz Socket AM3 125W Quad-Core Processor Model HDX945FBGIBOX - Retail
[url=http://www.newegg.com/Product/Product.aspx?Item=N82E16819103675][/url]

RAM:
OCZ Platinum 6GB (3 x 2GB) 240-Pin DDR3 SDRAM DDR3 1600 (PC3 12800) Low Voltage Desktop Memory Model OCZ3P1600LV6GK - Retail
[url=http://www.newegg.com/Product/Product.aspx?Item=N82E16820227381][/url]

Any help and/or advice would be greatly appreciated!
Thank You!

Thanks for the reply.
It's not an issue if it is actually going to noticeably improve my performance. I just don't want to shell out the dough for minute differences that I won't even notice.
I hear the 275 is a very good card. On Newegg right now though the 280 I linked is the same price...