I currently have both the 7500 and the 7125 and have used both in my main system over the years at different times. The 7125 is very capable and will provide all the power you should ever need for music or home theater. I originally bought the 7500 to be able to feed my Magnepans which are very power hungry. When the 7500 was in my main system I could not tell any difference in performance, but bear in mind that mt Klipsch speakers are very easy to drive to insane levels. You can expect about a 21 db increase in SPL from your speakers with the 7125 and about 23 db with the 7500. Given that you will rarely if ever drive your speakers to those levels( especially with the sub), you will have plenty of clean power to your mains and quite a bit of overhead for the surrounds using the 7125.
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Music system
Model 990/7500/Magnepan 1.6 QRs/Technics SL1200 MK2/Aperion S-12 Subwoofer/OWA3/Sony NS75H DVD
APC H15 Power Conditioner

TV System
Large Advent Loudspeakers/ Polk center/Monoprice surrounds/Panasonic Viera 42 inch/Onkyo HT-RC260/Sony BDP S590/Directv


Home Theater System
Onkyo PR-SC886/Outlaw 7125 Klipsch RF-82 L/R,RC-62 center, RB-35 SR/SL, BENQ HT1075, Outlaw LFM1-EX/OPPO BDP-83/Directv
Harmony ONE
Blue Jeans and Monoprice interconnects
APC H15 Power Conditioner