I think the 7600GT is a good choice, but it depends on what Hardware you have. I upgraded some months ago from a 5700 to a 7600GT. But I have a Pentium IV 2,8GHz and only AGP. It speeded up things dramatically (LFS not much, because it´s relying more on CPU than the GPU), but other Games which where not playable before are running very good now (the time I upgraded I played Prey, which was not possible on the 5700).
So if you have a old System like me and want to get the best out of it a Upgrade to a 7600GT seems to be the best choice if you don´t want or can not invest into a completely new System. I think the 7600GT in combination with my P4 is the best I can get now. I don´t think that a faster GPU will speed things up much more on my old, slow system.