I've had excellent luck with just plain old ordering from their website, parts being on my doorstep a few days later. *If you want to have a stroke, then order form FX airguns, that'll make you appreciate GX.
Anyway, I have two GX CS2 compressors and one CS3 compressor and they all are fantastic. I've used the CS3 so much, I keep thinking any day it will barf, but it just keeps going. I keep saying I'll relube it, but haven't yet, and it's been almost six months of fairly heavy use.
I'm sold on GX all the way. Simple, well built, don't get hot, don't need coolant, robust design, easy parts availability and reasonable pump speed for filling guns. I wouldn't mess with any other type of pump that takes coolant.
I just in the last few weeks taken apart two of my FX rifles, two HW100's, one Brocock and all have always been filled with the GX for several months now, and not a single hint of moisture in any of them. They were all spotless and I checked every nook and cranny. I also opened one of my other air bottles and it was also spotless too. I'm sold!