Trust me, if you're going to use a receiver as your preamp, don't get the one of the hotest running AVRs to do it. I'd take a long hard look at the Marantz receivers as they benchtest very well for their preamp sections and they aren't a stove either. Marantz receivers have a shallower chassis as well, under 16 inches. The Onkyo is closer to 19 inches deep.
That said, the Onkyo is a feature packed receiver that will likely satisfy your thirst for power without the aid of additional amplification. Having the TX-NR3007 juice your surrounds only is nothing to this receiver. The TX-NR3007 uses a triple darlington output stage which is one of the most robust forms of amplification that pretty much guarrantees A+ performance even with inefficient and tricky impedance curves of the most exotic speakers. To put it simply.... the 50 pound plus Onkyos are among the few receiver's I'd trust to handle full size electrostatic speakers. Short of the Yamaha RX-Z11, Denon AVR-5308CI, and maybe the top end NAD I wouldn't put much of anything else on ESLs
If you get the TX-NR3007 plan on adding some support cooling for peace of mind and better amplifier performance (cooler amp, less resistance, more power).
