I wanted so desperately to set up a system for myself to be able use with any PA for my own IEM mix using the Powerplay system from Beh'r, but the interface with the desk is the issue. an A & H mixwizard has direct outs for you to use, others you need a splitter box or snake. You end up taking too much gear to cover all scenarios.
The Rolls PM351 is great, but every now and then I would have phasing issues with my voice. I would turn my vox up on the Rolls box and it would cancel it in my ears fighting my vox in the FOH.
I went a little more elaborate and started using a Yamaha MG06 4 channel mixer.
ch 1 is my vox via a splitter box at the base of my mic stand so I can flip the phase to ensure no cancellation
ch 2 is a Rode M3 above drums so I can mix them in as often they are low in the FOH in smal rooms
ch 3 FOH feed - normally via the parallel out on the back of the active sub on my side of stage. If no parallel out, I use line splitter or Y cable
ch 4 feed from my bass amp.
I'm very happy with this set up.