I had an AudioSource Amp 5.3A for about two years. Unlike yours it was a monoblock design that I used for powering a center channel speaker. It never had a hum problem though, but it ran very hot, and I do mean hot enough to fry an egg. Finally, recently, it died after one of the power transitors got fried. I never ran it below 8 ohms, though it was 4 ohm capable. Now in retrospect driving a 4 ohm center would have been flirting with disaster.
After removing the cover, I was not impressed. The fan, which was very noisy, was a cheap 1.5 incher. Kind of a joke given too that the chassis was completely enclosed except for a few tiny vents where the fan was mounted. It took me awhile to find the blown component. The circuit board layout and architecture along with the wiring were a nightmare and very bunched up. The caps were very cheap including the filter caps which were only 10,000 uF at 80 V. I paid little for it, thus it's not worth the expense of getting it fixed. It served its purpose in that it convinced me that driving the center channel separately, instead of letting my Yamaha AVR do it, is the way to go to get better sound from a channel that is so vital to one's HT system. Despite its design flaws and cheaper components, it outperformed my 7.1 channel Yamaha AVR driving the center. I know that is a meaningless statement without data to back it up. However, I am only out to please my ears, not my fellow peers in the scientific community. My ears know it sounds better, though I can't prove it does on paper.
My center channel is hooked back up to my AVR now. It does okay for powering the surrounds though. I do miss the better sound I got from the center powered by the AudioSource. The front L and R channels deserve better too. So, I am in the process of finding three power amps that won't put me back a few thousand $ in debt. The Emotiva XPA-3 certainly seems ideal but the low price makes me a bit wary that I may once again be going down a similar path as before. I have no doubt that, just like the AudioSource, it is capable of producing great sound. My other options are find one that I know is prone to last for a long time like a Rotel, Marantz, or Adcom.
