I sometimes use resonator or banjo mandolins but prefer the sound (when I can hear it) of the regular one. (I was once asked, by a melodeon player some distance away, to play the resonator a little quieter - very pleasing!)

I'm just about to fit some pickups (from JJB electronics) so I'll heed the advice and experiment with an earpiece before risking one of the mini-amps.

Steve Shaw: banjos can be retrofitted with a resonator/reflector but not mandolins, I guess that's what you're thinking of.

Stim: these things don't have any adjustment except volume and, as an example, the minirig claims to have an essentially flat response between 100Hz and 20kHz.
I'm only calling them "speakers" because that's how they're marketed.

Mark: the top side?