GPS: TSO C129a, Class A1 (en route, terminal, and approach)

Yeah, your guess that he was referring to just the GPS portion is
correct. I've read about this "sole source" stuff in a number of places.
A non-WAAS reciever, as the 430s currently are, cannot be used as
"sole source" for anything except GPS approaches. Say, for instance,
that you're cleared along an airway. If so, you have to have a working
VOR reciever available and the VORs that define that airway have to be
operational (its in AIM 1-1-21). But, as you say, the 430 has a VOR
reciever, so you're okay (the 400, however, doesn't; it is just a GPS).
Maybe that's why airways aren't in the 430's database.

Now, if you don't intend on ever using VORs, you don't need a VOR
reciever, right? At least not outside of Class B airspace. In fact
where does it say that you need anything more than a wet compass and a
clock? And, if you can be legal with just a compass and a clock,
certainly you can't become illegal if you add an IFR GPS, right? So
what the hell does it mean, this "sole source" thing anyway?

Peter