I have just replaced a Bryston 4BSST (Front Left & Front right) and a Rotel 1095 (center & surrounds) with a P5.
The Rotel would have been an effective solution for all 5 channels, but was not as musical as the Bryston. The Rotel is great value 5 channel amp, and if its all you've heard you can live with it, but next to the Bryston it was very coarse. When I first connected the P5 it was detailed, dynamic and had a huge soundstage - but thought it to be much brighter than the Bryston. Doing an A/B comparison I quickly discovered the P5 wasn't bright at all - just very detailed, and much better than my beloved Bryston.
The P5 is really a great 5 channel amp.