Ooh, nice amp!

Dang, that's a good deal! I wonder why anyone would sell that beauty at a loss
For a pre-pro, personally, I'd wait on the inevitable Integra DHC-80.4 or whatever it ends up being called. The pre-pro based on the Onkyo TX-NR3010/5010 platform, in any case

Or you could just pick up a TX-NR3010 / DTR-70.4 / TX-NR5010 receiver and forego the internal amps in favor of the RCA pre-outs. The Anthem P5 is single-ended anyway, so other than canceling out any noise picked up by the very short cable runs between the receiver and P5 amp, XLR balanced connections wouldn't add any benefit anyway
Using one of the top tier Onkyo/Integra receivers also opens up the possibility of adding surround back, height and width channels in the future, using the built-in amps in the receiver to power those. So not a terrible idea to go the receiver route in any event
As for speakers, I'd be checking out some Focal Electra Be 2 setups, myself. Love me some of that Beryllium tweeter

Although they're fairly efficient and quite easy to drive, and won't come even remotely close to taxing that P5 amp of yours
