I was a 8500 guy too. It sounds awesome on paper, and I got one for only $90, but that was one bugged card. It has its share of hardware problems, like even though it should be faster than GF4 in Doom3 because of PS1.4, it is slower because of some internal quirks. Truform is mostly ridiculous. It entirely lacks MSAA and its SSAA is surprisingly disappointing even though it's said to be rotated grid of some sort. Its anisotropic filtering is fast but that's because it's very limited in quality. Backward D3D compatibility is poor. It is ok for most D3D7 and 8 games, and Quake engines work fine.
You guys really don't want ATI for your old games. But maybe you just want to mess with everything anyway.
RV250 is apparently more efficient because otherwise it should not be able to keep up with R200. It lacks the Truform hardware, somehow emulating it. It has only one vertex shader whereas R200 supposedly has 2 vertex processors.