It sounds like you're overmodulating your audio.
Open the Audio Mixer and watch to ensure that none of your music is peaking above zero or in the red zone.
Welcome to the forum.
Steve points up one very likely possibility.
Also, remember that most home theater systems employ what is called Bass Management. This can really get in the way with the mixdown. Most Audio engineers prefer to do a dry mixdown (such as for a commercial theater release), and just let the variable of the Bass Management end of things be set and adjusted on the consumer's end (lot of variables in those adjustments, that the Audio engineer cannot ever know), but some feel that Bass Management needs to be taken into account, especially if the consumer market is the primary target.
One way that commercial authoring houses will handle this is to offer two separate mixes for the Audio, and have it selectable from a Menu, or from the Audio button on a set-top player's remote control. This is exactly as is done with say a DD 5.1 SS Audio Track and a DTS version, on the same DVD/BD. To do this, one must have a full-featured authoring program, like Adobe Encore, as PrE's limited authoring capabilities preclude a primary Audio and secondary/supplemental Audio Track. Note: for NTSC DVD/BD, the primary Audio Track MUST be 100% DVD-compliant AC3, or PCM/WAV. That AC3 can be 2-channel, or 6-channel (DD 5.1 SS). On PAL discs, MPEG-Audio is still Optional, but that is rapidly falling out of favor.
In your case, I would look closely at the Audio settings, the Levels and Effects (EQ, Compression, Notching, Gating, etc.) applied. It is likely that if you are doing this in a heavy-handed way, then the Bass Management is really over-doing the processing in your playback system. Most Audio engineers will test with Bass Management ON, just to make sure that nothing is over the top, but will mix without it. It is safest to not do too much manipulation in the mixdown, as one never knows the settings that the user might employee.
If your playback system does have processing, there should be a Bypass switch to turn everything OFF. If so, try that, and monitor.
PS - Though for Surround Sound, this Wiki-pedia ARTICLE might give you some background.