So I'm Brand New to GMRS, but let me clarify a few things.
I Unfortunately do not yet own an SWR Meter, Working on that, so when i say power I didn't mean Wattage or even a measured amount of anything. I realistically meant the ability to hit other repeaters, reach people in the area, etc.
The Antennae in question was one of 3 that work roughly as good as each-other. I Have a stock 5(?) inch Antennae, a 48 Inch Antennae, and A 15 inch Whip Antennae, all of which work about as well as each-other. I receive and transmit better when I'm not using the AMP/UT72 Combo. I have yet to place another Antennae up to the U25. I am going to hook up the UT72 to the radio later today and see what happens. Maybe then I can diagnose it as being an antennae issue rather than an amp issue.
There was a while the microphone i was using was causing bad transmission, but I ended up using the radio itself instead, and that cleared up part of the issue. But even when I found the repeater, for Test purposes I used the radio right underneath and to no surprise got great results and got a repeater tail as well as a human copy. But when I plugged up to the U25 Amp, it almost seemed as a threshold more than an Amp, dimming the power instead of increasing.
TLDR; I don't yet have a way to measure power, but after testing the radio in the field, the radio by itself transmits and receives better without the U25/UT72 Combo.