The beauty of using professional amps in a home theater/residential setting that many in this thread are overlooking is the availability of input voltage attenuator knobs. Few if any amps marketed towards residential/HiFi use have the ability to optimize gain stage at the amplifier level. Optimizing the source output voltage with the amplifier input voltage is a total crap shoot in most cases.I have a CT8150 I am using at the moment and I find it to be quite good… and fanless.
I think your bar of 60dB is too low IMO. It seems to me it depends on a few things..
-How much of the SINAD (THD+N) is noise vs distortion. Noise is easy to hear.
-Listeners volume level. If you are listening at low volume, Low SINAD just isn't going to matter much all. Put a SINAD of 60dB that is noise dominated at reference level, it can certainly be a problem
-Sensitive speakers-put a SINAD device of 60dB that is dominated by noise on some highly sensitive speakers, can be a problem
-Room-Some people listen in a noisy environment like a living room with a high noise level. It is going to be hard to notice. However, many have went to a lot of trouble to have a very low noise floor and in these rooms noise can be very noticeable. For example in a well designed theater room, you can have 16 speakers, some within 3-5 feet. Hearing noise during quiet passages is not what you want to hear.
Does a device need to have a SINAD of 115dB to be transparent for everyone's use? No. But a SINAD 60dB in many circumstances will not be audibly transparent.
In my setup I use an AVR with user adjustable output voltage - set it as high as possible for undistorted ouput (thanks to the testing done by Amir)- then dial back the voltage with the input voltage attenuator knobs at the amplifier to eliminate any noise floor issues using high sensitivity speakers (in a room built for low noise/~NC20).