What console are you using? If there are enough outputs to serve the IEM TX's, and it's digital and has a mobile app, invest in iPads or tablets to allow the musicians to mix their own. I feel the personal mixer application is going to fade as more churches get digital consoles that allow a tablet to do the mix. Every channel on the console is available, as opposed to the channel count limitations of the PSM systems. Also, the musicians can share tablets to control mixes as well. At my church, people are free to bring their own device, or we have a couple iPads on stage that they can walk up to, select their mix, and make the changes they need. If you're still running an analog console, it's worth looking at the cost of the entire PSM system, and comparing it to the cost of a digital console and a couple iPads. You might be surprised that you'll find more bang for the buck going with the digital console.