The B&K amps and receivers run hot by design. They use MOSFET technology, and that tech requires the amp to store up more energy than it needs so it has plenty of power to back up those thundering moments in a movie, or in your music. The reason an amp is putting out heat is because of wasted energy. The amp will dispense any unused electricity by way of heat. When the B&K or any MOSFET amp is at idle is will be very hot, but when you start to crank it up and use its power the chassis will become cooler.
Not all amps work like this, Sunfire amps use a tracking down converter to track the audio single, the Sunfire only consumes about 7 watts more then it needs, wile I believe the B&K is around 32watts.
I have tried one of B&K’s little 125.5 amps and did find it to be a grate space heater and a nice little amp, but its sound was artificial and lacking warmth. The Sunfire Cinema Grand gave me that worth I was looking for but I lost the big bass. The Sunfire may be rated for 70 amps of current compared to the 125.5’s 30 amps, but the B&K was far better with low-end bass, I have to crank the sunfire way up to get any ware close to what the less powerful B&K could do.
As Roberto says “Trust Your Ears”
I was told that was 'normal' heat disbursion. Just how the class "A" AVR's worked... I was to discover later, B&K's run hot, because of how they are desinged and ML's draw so much from them, when playing, especially the AVR's... I also discovered that Magnolia Hi-Fi, pushes the B&K's gear, at there stores. IMHO, for my ears, the B&K AVR's as well as seporates were too bright and brassy with ML's. I would recommend that you audition more prespective gear in your own HT. Ask to take it home over night and see how it sounds in your system... 
