Your best bet is to call them all and ask what they do for the service cos one place might be 50 bucks cheaper than the next but they might not for example clean your throttle body out when the other place does.
I think most of us here have learnt that cheaper isn't usually better.
Otherwise make your choice like this, NOR Racetorque or SOR RMS.
I agree with Tuna, none of the usual wrx places won't get too excited at driving a bugeye so no chance of it getting thrashed.