I've noticed a significant difference in bass levels from my subwoofer between 2-channel modes (stereo, bypass, upsample) and multi-channel modes - specifically Prologic IIx Music. The bass is significantly louder when playing the same source using Prologic IIx Music mode. I tend to prefer the extra bass as I usually listen at lower volume levels but sometimes it can be a bit much. When I switch to 2-channel mode the bass level decreases significantly - usually too much.

Why is this? Is this a feature of Prologic IIx Music mode? Should this be happening or should the bass levels be relatively the same regardless of using 2-channel or multi-channel modes?

BTW - I've level matched my speakers to 75db at 0 volume level with the sub between 80-81 db. All speakers are small with appropriate cross-overs (60 for fronts, 80 for center/surrounds).

Any thoughts?

Thanks!

Bryan