abefroeman said:
If I buy a receiver with pre-outs such as the ONKYO TX-SR503, and I use a power-amp for the mains, do the rears and center have more available power?
Yes, when all channels are driven.
Most, if not all HT receivers, use one power supply transformer with multiple windings for each channel. If you use an external amp for the mains, the receiver's power supply is relieved of that burden, leaving only the power requirements of the center and rear speakers. It should handle that easily.
Onkyo is among the more conservative at representing its amps power. If they claim 75 watts/channel when the two main channels are being driven, it is more likely to be true than many less costly receivers that claim higher power. Why not try using it with your speakers and see how it does, before assuming you must have more power? If your speakers have 4 ohm impedance, you probably will need that extra power.
