I've got an ACI Bulldog, which is a fixed-output regulator giving you about 850psi. For me, the thing works great. It's consistent and just fly. (Ladies dig Bulldogs, dawg. Woof.)
But is there really a "best" system? I don't think you can go wrong with most of the current selection out there, like PMI's Pure Energy or whatever...
Just pick a pretty bottle and cuddle it often.
Look for the usual spots where to get it: actionvillage.com etc.