On occasion I will do a gig with a guitar player or singer, and depending on the size of the room, I'll either use a HK Nano, LD Maui, HK Element, or RCF Evox, (1 of the few pluses of owning a store) I almost always seem to gravitate towards using the PA4x, but one of the great things about the PA4x is the ability to use the PAAS system to hear my mix.

I end up plugging in my duet partners feed into he aux in on the PA4x

then I mix it together until I get the mix I like coming through the PAAS, then from there, I'm pretty sure the sound coming from the PA speaker will be perfect or close to it for the audience