Mag valves will take quite a bit more than 900 psi mate...think nearer 3000.
The valve itself is just a regulator...almost identical the Armageddon reg, which is a bottle reg.
I had 1200psi in my RT once...bounced like feck...was brilliant...was just saying tonight to Fly, they just dont make guns like that anymore...what gun do you know of that you could put 1200psi into and still work, let along work better and not blow up in your face!!