Man, you could have gotten a better amp on our classifieds for 300$.Don't ask.... haha. Close to $300 inc s/h and taxes.
I'm not trying to break your balls, but I'm just giving you a helpful suggestion.
And I like the fact you are asking questions and want to get things right the first time, most noobs will think they know it all until problems arise.
The HU will be good to use, however the Sony amps tend to break easily in some cases, and from what I've heard their distortion percentage is more than they advertise in the specs. As for subs, MTX is alright I guess, I've never personally owned one, but I wouldn't spend my money on it. Like I said the classifieds will help you get louder for less money.
