By adding the MC402 you'll get a more dynamic sound than from the 6900. You're adding 200 more watts of power so it'll be able to control you're speakers a lot better....On a side not Lrsky on the 402 and 6900 they have autoformers...it doesn't matter what ohm load you spec it out at ...2,4,8 they're all 200w on the 6900 or 400w on the 402
