Originally Posted by
boputnam
Bullshit. There should be no hiss.
The hiss is only noticable (audible) in the HF, but my grab is there is noise throughout your signal path - you have a very high noise floor. You talk of trialing all manner of xovers and no change. My guess is the noise originates BEFORE the xover insertion point.
QSC's are not the problem. Stay with the pro amps.
Can you trial another player and preamp unit, like Heather suggested? I mean hell, I've used all manner of consumer gear but the thing that totally ruined me was a lame Onkyo consumer-grade preamp. That said, all it had was a poorly grounded (designed) power supply, but there was no hiss.
I'd start at the beginning of the signal path. I think your problem is rigth there, and not related to a GL (balanced vs unbalanced).