Greetings.
Im guessing your gonna pay about £230 for your marker?
If thats the case, you dont want to be spending £300-£350 on an air system thats adjustable because you dont need to.
I have an RT Automag. When my govnair lets me down I might get an AA Melee. These are about 800-850 psi fixed output.
You can get HSE 1.1 round bottom Luxfer tank on one of these for about £165. The good thing is, that AGDE (Airgun Designs Europe) make them and their customer service is second to none, I was there today and John Sosta is a very helpful man.
Call Jackie or John on 01206 240 831.
The other good thing is that, with the screw in tanks, if you run out of air you can just bung a 20oz co2 on and off you go.
If you get a flatline(very good, but not necessary) or max flow you cant do that, as the reg is fitted to the gun and doesnt use a bottom line ASA.
Hope this helps.
Gaz