I run sound for every concert in our church, in addition to running sound for dozens of shows over my career (though I'm usually on the performing end).
I still think we need more info.
What is the OP running Garage Band on at home? If it's a laptop, and if I understand correctly, could the OP bring and use the laptop he has at home, with the plugin in Garage Band that makes his in-ear monitor sound better, then take the output of that laptop into the church PA? That takes the sound engineer out of the loop, by sending him the signal the OP wants to hear and does hear. If the OP does not have a laptop at home, is it within budget to get one?
Yes I running into a MACbook pro at home which I was thinking is obvious since I'm running GB. Perhaps I'm not explaining myself correctly. This has nothing to do with the tone that's in the house. I wear in-ears so I could care less. The whole problem is the guitar tones coming from GB into my headphones is fair superios that what's coming down to my pack at church using a very expensive Midas board. I'm trying to get the in-ear tones at church as good as they are at home. Which possibly means, having the sound guy add something inbetween the board and my ears or maybe there's something I can put between the Kemper and the XLR cable that is taking my signal to front of house. Hope that make sense. But the main problem is the guitar tone at church is nowhere near as good as it is at home and it's because of this ambient vocal effect that's inherent in GB. Hopefully that clarifies things. If not, I'm going to just drop it. thanks.