Real life performance differences of multi channel amps depends on your application and supporting gear. Most of the modern multi channel amps are built for HT duty. They do a nice job of powering the sound of the chop of a helicopter blade or the impact of an explosion. The power ratings in 2 channels driven versus all 7 may be because in normal HT use, rarely, or only in very brief moments are all 7 channels be driven equally. Usually only the center channel is driven continuously. So, in their mind, continuous RMS across all channels is less important? Ultimately it comes down to how it sounds in your system. Specs can’t tell you that. But do not assume these types of amps can sound as good for 2 CH music as a dedicated 2CH amp designed specifically for music reproduction. Different applications, different design goals. So if music is at least one of your priorities, get a dedicated amp for your mains, maybe a decent integrated amp with HT bypass. This should help maximize your music experience. And then get whatever you like to power the rest for HT (or other) duty. If you are comparing between multi channels amps, you need to level match the volume from one to another. When you A/B them correctly, differences in HT applications can be less significant than you might expect.
Difference between amps
OK so let's talk amps. I'm sure this has been addressed before but are there real differences between multi-channel amps among the various brands in the mid-fi to high end markets with comparable specifications? Adcom, Anthem, Classe, Emotiva, Krell, McIntosh, Marantz, NAD, Parasound, Outlaw, Rotel, etc. What are the differences in these brands? I can site one difference. In multi-channel Marantz amps, the specs never state "all channels driven". They are notorius for misleading the consumer with their power output ratings. But that's a marketing decision. What are the real or should I say physical or performance differences among these? .