I get the impression that Dave's business (Power Modules, Inc.) is pretty much a 'Mom & Pop' shop. I know that he personally did the work on my amp, and I suspect that's the case with each piece of equipment that comes through his doors. If he fails to answer the phone when you call, or is slow responding to your emails, it's probably because he is BUSY WORKING!
I'm more than happy to accept the occasional slow communication with Power Modules, Inc. in exchange for the satisfaction of knowing that when I do speak with someone there, it'll be the man holding the soldering iron.