he panel mount Garmin's display and functionality is so vastly inferior to
the AvMap, that I would certainly look at *it* as the back-up unit -- not the
other way around.

Yes I love the ease of read with the Avmap
However it would not be legal to fly approaches with it.
I do not have DME and a lot of approaches
require DME or GPS. I thought about installing the Garmin 430, but the 480 is
only 2K more.
To upgrade the 430 for Vertical and horizontal capability will be 1500, if and
when it becomes available.
Hank