Is the x850 xt a better card even though it has shader 2.0 and the x1600 has shader 3.0 and that the 850 is on direct x 9.b and cant go to c and the x1600 is on direct x 9.c
As mentioned, it's a highly deceptive thing, the X1600pro. Yes, it has SM 3.0 support. However, it's about as powerful as the GeForce 6600GT. Yes, it has 512MB of RAM, but that's largely moot.
The fact is, the X850XT has roughly twice the graphics horsepower you'll get out of the X1600pro, for about the same price.
If you're worried about HDR, a number of games have HDR options for SM 2.0 cards;
Splinter Cell III was mentioned, and
Oblivion, thanks to it's easily-modded state, has a mod that allows HDR for SM 2.0 cards. (on the flip side, it also allows GeForce 6 and 7 cards to use HDR with MSAA)