Well, it's either an expansion chamber or regulator, not both.
I would go with a regulator, clamping feedneck, on/off asa, maybe a barrel kit, freak, pipe, whatever you like. Electro Hopper, and an electronic frame if the Elite doesnt already have one. If it does, you can always upgrade to a Tboard and then add eyes.
There's a lot you can upgrade for 300 bucks.