Thanks for the advice, Steve. I have read over both products and, I believe, visited your excellent web site. Perhaps I've spent too many hours by the side of the road with the hood open tinkering with this or that to want to have to rely on having a laptop handy. Plus I'm a MAC guy and just getting near Windows makes me break out in hives. So I've pretty much decided on the pricier but simpler-to-tune SDS system. I've also had excellent response to my email inquiries from them. That gives me confidence.
I'll try to do a full report on its installation.