First, am very surprised you are having trouble with Nuforce repair person. If it is who I am thinking of, myself and many of my friends who have Nuforce amps have received excellent service from him as recently as last week. PM me for his name. I love my Nuprime Ref 20 amps, but have auditioned many respected brands of class D which I found not as good as the Nuforce/Nuprime sound, so make sure you can have an audition before purchase.