cheap, they are
durable, they are
powerful, they are
low noise floor, they have
low impedance drive capabilities, they have
uniform output from 20hz-20,000hz, they have
balanced and unbalanced connections, they have
Rack mountable, they are
hidden, they could be, if necessary
Yamaha pro amps for the win.
There is absolutely no reason not to purchase a pro amplifier excluding three reasons
1.) you can't stand the appearance (no big deal here if all you care about is the sound quality)
2.) some of them have fans, the Yamaha's rely mostly on convection cooling with fans as a backup (and you have to be pushing them extremely hard for extremely long periods of time to get them to turn on, it's likely they never will)
3.) you have a mental block about the mystical world of audiophiledom, and get hung up on all that non-sense those weirdos with ERS paper and musical, enthusiastical, danceable, several thousand dollar cables that there cryogenically frozen and sent into space for 10 years, later retrieved, and sold to the unsuspecting audiophile that thought it would give him the dead cold accurate, yet open, sound they where looking for.
If you ask me the last reason usually doesn't affect people here, we like to keep sane.