Crutchfield is great don't get me wrong. But all of their items are retail.
Personally, I find what I want and read the reviews on Crutchfield, then buy of amazon for 20ish% less.
Kenwood DD FTW!
I'm not a "tuner", I am a ecu software engineer. Its different.
2011 GT500 = It gets me from A to B If you want good technical help. Put your Year, trim, engine, and PCM code in your post! Its easier that way