VERY COOL!!
Thanks for the link. That would help a lot.
I'm looking at the smallest powered monitors from Audix:
http://www.audixusa.com/docs/specs_pdf/PH3-S.pdfThese will run on 12 volt, but with a little less power output, or full power through a power inverter. (Or so I was told when I emailed the company.)
I was thinking of putting a piece of velcro low on the A-Pillers near the top of the dash, one on each side, to keep them in place on the road. Fortunately the top of the dash on my delivery van is flat and roomy. (I need something small and portable and easily set up / torn down. I can't leave it in the van overnight.)