How much are you paying for the pack to carry that tank around? Buck up, drop the stock, use the tank when you shoulder the gun, it won't kill you. It'll also save you some jack.
I'd second the Invert Too or even a Vic35 Halo-B over the Rotor. The Rotor has some nice features, but the Invert Too for a third of the price is tough to pass up.
The barrel, everyone thinks that want one of these uber-range enhancing barrels before they play a lot of paintball and learn that it's not that important. I'd suggest you play a bit with the basic gun/loader/tank combo before starting to heap on upgrades.
Could we spell it correctly...please?
Take a look, you might be surprised.