My band bought several of the Carvin EM 900 systems. We got one used for $300, and 2 more on sale from Carvin at $350. They have gone up to $429 now. They work ok. I can't say I'm thrilled with the sound quality though. We get some RF noise, especially our singer who uses a wireless mic - that causes a little noise here and there.
For me, it's ok. I have a wireless system on my guitar too, but no real issues that I can't deal with ( a little static here and there... not too bad.) I am using the stock Carvin ear buds, and they lack bass response. Overall, the sound of these things is a bit thin (with any headphone I have tried.) There is a big difference between plugging headphones into a source straight and routing through the IEM system. But they get the job done for a low price. I'd like to try out the Sure PSM900 to see if there is a real difference in quality of sound.
We have an Allen&Heath QU-24 board, so everyone gets their own mix, and they can control their own mix from their phone or tablet, which is great! The board gives 3 stereo + 4 mono mixes, so we can run 7 different mixes. With a little smart sharing of mixes, everyone can have stereo if they want.
So, to answer the OP, I take my mix from the board. I also have 2 CLR's in front of me that I control with a line mixer in my rack. (so basically, I run both stage monitors and IEM's. I have a choice. I don't need both, I can go either way) I really only need the CLR's to give me a source for feedback, but with my line mixer I can get my vocals, guitar, and the band all in my CLR's if I wanted to.