Amplifier and sub problem

Hi guys.How are you?I need professional help,that's why i am here.I have couple of questions.i better will start from the begining....i have

bought some this Alpine's products:mono  amp MRD-M300,15"sub SWR-1541D, 4ch amp MRV-F340, front door speakers SPR-176A, for rear shelf SPR-694A, head unit Sony CDX-M730 everything in a Mercedes A-class.1)I have installed a 15"sub and mono amp.I set up amplifier the way Alpine recomends(from Alpine's site PDF file"Maximize the output of your MRD-M300/MRD-M500")and now even at low volume it seems that it's playing with "distortion".I know that Alpine recomends MRD-M500 amp instead of MRD-M300 but i cant through many awayi have already bought MRD-M300.I don't know what's wrong.May be you guys know any different settings for this amp.or something else what could be a problem or may be ....i don't know what to think of..

2)I didn't install the second amp for my front and rear speakers.The amp is like i told MRV-F340 Head unit Sony CDX-M730  Will i gain anything by installing this 4ch amp for front and rear speakers?

/ / / / / ALPINE

The only thing i could think of that could be wrong with the distorsion is the way you ran your wiring. You need to run the power and signal wires on opposite sides of the car. So run your RCA's and the remote wire away from the power wire. This happened to me and that was the problem. However, it may be something else that i dont really know of.