You need surround sound to enjoy the game fully. I have 5.1 headphones.

I don't have a problem with framerates...my Geforce 6800 runs it pretty fast at 1024x768 with 8x AA and 8x AF .

As for the choppiness, that's a hard drive related issue. To fix it, go into the Doom 3\base folder, and open each .pk4 file with WinRAR, and extract them into the base folder. Then delete all the pk4 files. You'd easily gain 10 fps on the game because now the cpu doesn't have to decompress the game files every time a monster pops up. Be warned though, decompressing them makes the game take up about 4 gb of space.