I believe all the aftermarket coils do is lighten your wallet.
I'm making close to 690hp at the wheels useing stock coils, the guy who built my motor(ric3xrt) is making 740hp to the wheels in his solar yellow GTx ,with S.O.S coils , 720hp in the Purple GTx with stock coils.
I know he's done some dyno testing MSD vs 09, Vs 6.1s vs Accel and SOS , stockers and S.O.S made a few HP more then MSD. ACCEL were about the same as the stockers maybe a Hp off, I'd have to ask him..he's hard to get ahold of now adays.