have you looked into kenwood HU's at all? I have last years mp919 model, which has cut off frequencies for front & rear speakers as well as for the subwoofer. It also has a built in "gain" for the sub, as well as a button that mutes the sub altogether. It sounds really good once you get past all the eq settings. The only thing with their 2003 HU's however, is the styling - kinda ugly IMO.

I'll agree with you about Sony though, I had a Sony HU crap out after 9 months of owning it, that was the 1st and last time a Sony product gets in my car.