1. The highest 3DMark2006 score for a Mobility Radeon X300 on ORB (Futuremark's online database) is 438. It was done on an Inspiron 6000D with a Pentium M clocked at 2.26GHz. The video had an engine clock of 420MHz and a memory clock of 308MHz.
2. DST is not supported in any ATI Radeon product prior to the 1K series (13xx, 14xx, 16xx,18xx and 19xx)
3. You can check the level of Direct X support by running DXDiag from start|Run or if you have the DXSDK installed you can check the caps viewer and it will tell you the exact level of Pixel Shaders your GPU supports