Unless you really care a lot about higher quality surround processing and have very good/expensive surround and center speakers, I'd use a decent AVR for processing and driving those channels. Buying a prepro that significantly betters a decent AVR for processing along with the added amplification you'd need to buy would be a huge added expense. But if surround music/movies are that important to you and you have the speakers that can benefit from it, it can be a perfectly justifiable purchase.
AV Pre/Processor vs 2 Channel Pre-Amp - Sound Quality
Ok, so let’s say we have the most amazing separate 2 channel amp, and we connect it to an AV Processor, and then to a dedicated 2 channel preamplifier separate specifically for music play. Are we really going to hear a difference at say the $2000 level?