factory hu

I'm redoing the audio in my '07 Mazda3 Hatch and I'm not sure what interface I should get for it. I want aftermarket sound without replacing the factory unit because it just looks so **** good. I was looking at the MTX Re-q5, but I'm worried about alternator hum because the outputs are less than...

how do i get it out without having to take the new one back out and pluging the factory wires back in ?

so ive had my setup in my 08 civic si with premium sound for about a year and a half now. i have an loc installed where the factory sub used to be. ive went through 3 subs so ive started to do reasearch. ive recently figured out how tune my amp with a dmm. now im wondering if i can check the...