Thanks for the replies so far – I do in fact sing, and on several of the duo jobs I've done with a singer, I've used the CP4 split playing LH bass, with a Roland BK-7M (only using the rhythm element of any styles, as I find those VERY cheesy) and providing backing vox using a TC Helicon Voicelive. Together, it sounds quite good but it's a pain to bring all the different units and wire them up etc, and there are three different pieces of equipment to keep on top of. Something like the PA4X would replace the Roland and Voicelive, so I could raise a bit of extra cash by selling those too.