Forgive me, I'm a newb to practical Ambisonics myself (just starting
to play with it, had mostly been just familiar with the theory in the
past)...
Nothing magical will happen if you pan the 5.0 signals
into
a 3rd or higher order AMB system. The results is just five
virtual speakers reproducing 5.0.
Do you really mean third order ambisonics, or do you mean
three-channel first-order ambisonics? I had been under the impression
that it was unusual to run across actual high-er order
recordings/playback systems and that most of the installed base was
first order.
Cheers,
Monty