Re:
Hello,
If you haven't done so, go into the EAX Console > Speaker Settings and do a Speaker Test.
If the output to the speakers are correct, then it's not your soundcard or speakers.
Go into Winamp, Preferences, then click Output under Plug-ins, double click DirectSound Output in the Output plug-ins box and make sure Allow hardware acceleration is checked. Also, try changing the device from Primary Sound Driver to SB Audigy Audio 2...then check to ensure that the Device info box shows Speaker setup: 5.1
Report back.