I bought my AP from Stein, even though I had to pay sales tax to do it.
1. They KNOW this stuff.
2. They make most of the commercial wiring harnesses and their color coded premade harness makes wiring a breeze.
3. Great service.
4. Competitive pricing. I doubt that they are the absolute cheapest, but they have really helped me, even to fix screwups, even when I caused the screw up.
Lots of low buck suppliers come and go in the experimental world...Steinair is here to stay and all the guys there are experts...most are former Airline engineers, and airline simulator engineers/techs.
JMHO