I attempted using external amps for the mains via a 2ch preamp (no tone controls) with HT bypass and using the AVR's internal amps for the center and rears. My Yamaha RX-V475 doesn't have 5 ch preouts and the one audio out doesn't have any signal with HDMI sources. Do to limited cabinet space I'd like to stick with an AVR rather than get a processor and a 3 ch amp for the center and rears. So would an AVR with preouts likely do what I want or would it be all or nothing? Would the auto room correction/setup likely still work as well? Caveats?