Help with soundcard.....

I have a Dell XSP 400 with a soundblaster X-fi Extreme Music soundcard. I recently upgraded my speakers to the Inspire T6200 5.1 surround sound speakers and bought the Creative Fatal1ty headset (the one without the usb) and since I have installed everything, I get great sound through the headsets and the front speakers, but the Microphone on my headset sounds muffled and the center and rear speakers sound muffled as well.

I have Windows XP media center edition with an Intel 4 duo core 2.80 GHZ processor. I'm not sure if its the speakers and the microphone on the headset or something isn't configured right on my system. I have gotten the current drivers from creative labs and their troubleshooting doesn't help much. Any suggestions would be great!