[Medic3]

So I recently bought a Used 07 335i Coupe with the Logic7 Sound Package. I believe I might have messed up my Amp though. I listen to my music at a pretty high level compared to most, now my speakers have a crackling going on, and I'm stuck listening to the radio since my ipod sounds like garbage now. My problem is I don't know where to begin I keep reading different post but nothing quite gives me the answer I'm looking for. I guess what I'm trying to ask is what is my best option. The audio guy I go to said it could be possibly the AMP giving out improper signals or my HU. I have a aftermarket headunit but from what I have been reading there is no easy way of installing it. Any advice would be great.