I have just installed sr6500 components powered by an alpine pdx-4.100 amp. It sounds incredible, and the bass is pretty good, but is lacking the depth of a larger speaker(ie subwoofer). I'm trying to decide between the sr104svc and sr124svc. I will be powering the subwoofer in a sealed enclosure with an alpine pdx-1.1000 amp. I'm looking for SQ as opposed to SPL. I see the sr124svc has a slighly lower frequency range and was wondering if it makes much of a difference. I can afford the sr124, but I am wondering what justifies the differences in sound quality, so please no "if you can afford it, buy it" responses.