Originally Posted by Pr0ph3t

I'd say save all the money you'd spend on upgrades other than nitro and a new hopper, and put it towards a new gun. Quite useless to put that much money into a stacked tube blowback, but if you still want to, go with the following:

1 - A nice sized nitro tank (preferrably a 68/4500, they go forever, and fiber wrapped)
2 - A nice regulator
3 - Electro hopper (eggII would be your best bet, or a HALO, but I dunno if it would feed past the detents on a fish)
4 - E-force trigger frame
5 - New bolt
6 - Barrel (J&J, CP 1 piece, Teardrop)
7 - ....new gun.