I am going put new components and a sub in my Porsche boxster. My question is should I get a 4 channel amp, run the components off of the front 2 channels and run the sub bridged off the other 2. Or should I buy two amps? I am going to run a set of 5 1/4 diamond d6's-85rms and a 10" diamond d6 sub-500rms. I was thinking of getting a soundstream picasso 640.4. Would this work or should I have two dedicated amps. Thanks in advance.