If you want wider bandwidth for memory then get the 8800GTS, that's not that expensive now. These cards should be pretty cheap so you have to make sacrifices somewhere. As games go more shader based rather than textures then it would pay to concentrate on the gpu, but there will always be a trade off.

We need to see the benchmarks before saying the 128bit bus is a bad mistake for a midrange card.

Having said all that I am in no hurry to upgrade from 7900GS to one of these at the moment.

Regards
Andy