Sorry to hear those aren't working out, thanks for the information. I never did try any of those Audiosource amps. The "good" reviews I had seen were for long-discontinued models, like many companies they possibly went on the long slide down to cheaped-out products to try to eke out more profits. A losing game IMO.
Knowing what I do now after that old thread, I would recommend saving a little more than that $500-700 budget, and without any doubt buy a used Bel Canto eVo amp on Audiogon for $750-850. Cost about $2600 when new a few years ago. Very likely the last power amplifier that you will ever need to buy, incredible sound.
When you get a chance, for sure try a pair of Zu Audio
speaker cables. These can produce a great improvement in the sound of any amp/speaker combination.