As everyone has already pointed out: The less noise, the better (obviously), both in the preamp and in the poweramp. Generally speaking, surround receivers are horrible when it comes to noise, so you might consider stepping up to a better unit or a dedicated high-quality surround preamp. However, even with a low-noise preamp and a low-noise power amp, the noise can still be audible since the gain of normal pre-power combos is tuned for much less efficient speakers than Klipsch. The solution is, as several people have already mentioned, to reduce gain in the power amp thus forcing the preamp to output a higher signal (using more of the dynamic range). For some strange reason, very few power amplifiers have a gain switch or potentiometer. In the old days (80's to mid 90's), most power amps had a gain potentiometer: Denon, Sony, Luxman, Accuphase, McIntosh, etc. The only power amp brands I can think of today that have a gain switch are Accuphase (I have one, it works great at -12 dB) and GamuT (selectable gain using jumpers on the inside of the amp). Do you know of any other brands? Could it be that the vast majority of power amp buyers have inefficient speakers (sensitivity around 90 dB) and that the audio electronics firms concentrate on them?
By the way, has anybody tried the Rothwell in-line attenuators? You can find information about them here:
http://www.rothwellaudioproducts.co.uk/html/attenuators.html
http://www.enjoythemusic.com/magazine/equipment/0803/rothwell.htm
I'm a bit sceptical towards attenuators since they can affect the sound, though. Does anybody have any experience from introducing attenuators in the signal path? I think they must be of high quality in order not to degrade the sound.