If you're going to spend that much money upgrading a 300 dollar marker, why not wait and get something nicer, like an Angel (led's are about 500 now)! Now that that's out of the way...
My buddy has a bushy that he wasted a fair share of his money on, so I'll give some suggestions based on his experience.
Buy either a freak or a boomstick if you want a great barrel.
A stabalizer would be kinda pointless, they're better suited for co2 than air. Everybody who has bushys usually buy gladiators.
A new chip will only increase your ROF by about 4 bps, so it's up to you
New bolt's a good idea, helps alot.
New valve can help, not a neccesity, but if you think you want one...
My buddy never had any blowback into his feedneck, he used a ricochet 2k and it worked great for him, if you want an over-inflated balloon sitting atop your marker, the evoII is for you. A 12volt rev with x board should do you right fine.
An LPR guage can be helpful too.
The system X drop/cradle is really good, if not that, the shocktech.
If you're playing front, a new feedneck would signifigantly lower your profile with a bushy.
The crossfire is a right fine air tank, but why do you want a 47 ci 4500psi? A 68 3 would be smaller and give you about the same shots
Good luck