I thought about doing something similar with this,
THE T.MIX MIX 1204 FX - U.K. International Cyberstore
So they could even have reverb on their vocals if they wanted. In the end though my tech and I have designed a system ourselves from scratch. There has been a fair bit of R&D and prototyping but we are getting close to the end. It will have,
6 mono inputs with pan
1 stereo input
Talback mic with level control
Class A headphone amp, loud!
Intergrated stand, 2 heights for standing and seated musicians.
I am using these to split 8 outs from the console 4 ways, maybe you could use something similar too??? They sound just fine, I will open one up all the same and see if there is anything that can be upgraded and improved. I looked into building a splitter but you could barely buy the XLR's for the price of the whole unit!
MILLENIUM SP 8 SPLITTER - U.K. International Cyberstore
We have a prototype built which sounds really good and I hope to have the whole system built and up and running in a few weeks. At the moment I am building 4 mixers but it would be easy to expand the system to 8 with 4 more mixers and 4 more Millenium splitters.