For 500bhp the GT30R (ie the 3076R) would be fine, the others for more than 500 really.

Both will need external gate, modded downpipe, etc etc, but would be fine.

Looks to me, considering they are using all their pics etc, as well as offering the exact same (and in most cases exclusive) options, that they are probably just buying them from ATP in the states with a trade account, and then selling them for a profit over here.