I recently bought an Audi and the speakers are shot. I purchased INFINITY KAPPA 50.9CS 5.25" & INFINITY KAPPA 60.9CS 6.5". I have a sub and am in the market for a 5 channel amp. My question is: will a stock head unit work with all this or will I have to go after market? Also I want to hardwire an AUX in with a 3.5mm plug for my phone, is this possible on the stock head unit? Thanks!