Hi,
Like other players, I have noticed performance degradation since 0.25 came out. After hearing the main game music playing in canon*, I disabled the music entirely. Turns out this was the biggest performance gain I got out of the game. 
Unfortunately, I'm not home right now so no dxdiag. (I have a dual opteron 248 with a 7800GT, a pair of raptors and 2 gb ram, running XP -- not a bomb but hopefully adequate
)
Jaye
* canon: Not sure if this is the right English word. Essencially, the same music track was overlapped with an offset. I have no idea how this happened.