As for the motor, am not sure how well is the 7mge going to hold compared to the turbo model. The 7mgte should handle 500rwhp safely on stock bottom end and head, aside from a metal head gasket and arp studs. Just supply it with enough fuel and a big enough turbo, you shouldnt have trouble making about 500rwhp.

You could go na-t, but keep in mind that 7mgte/transmission and ecu shouldnt cost much.