I just recently switched over to linux (gentoo), and my soundcard isn't working to its old standard. I have the emu10k1 module compiled into the kernel, and the sound works fine, but the center and both rear speakers of my Creative T5400 don't output any sound. I have checked the cable connections, and they seem fine. The front left and right speakers work, although the sound they output isn't very good quality, and doesn't sound anything near as good as it did on windows, with the same music files.

Any ideas on how I can get the soundcard/speakers performing a little better, and getting the center and rear speakers working correctly?