Hehe, its okay. I should have actually done what you did, as its alot more confusing the way I did it...
Yeah for standard resoloutions like 1280x1024 with some Antialiasing and Antistropic Filtering, the 7600GT would probably be fine for the latest games.
If you want higher resoloutions though, the 7800 range, or even the 7900 range (can cost around £155 now surprisingly) will give you an extra boost.
Of course, if you want to buy a card that'll last a while, and even through some part of Direct X 10 (hopefully...), the 8000 series is the way, and of course, the most expensive route to go.
I'd personally like MikeReiner says, buy a card now that'll suit Direct X 9 games, and when Direct X 10 starts to be used alot more, buy the 8000+ series that'll perform well in those games, which would have then dropped in price, but still be thouroughly capable.