Do you have RCA pre-amp outputs on your SONY? If so, just buy a 4 or 5 channel amp (
Alpine 5 channel with built-in crossovers for $200), and quit running your system off of deck power. I don't recommend running on deck power anyways, because the amp section of the deck generates too much heat, and so does the laser of the CD reader head, not to mention the heater from the car's heater ducts are all under the dash too, creating extra heat. The Alpine amp would nestle nicely under the seat or in the trunk (way cooler). I'm running my 5 channel amp's 4 front and rear channels off of the STOCK front and rear Contour speakers (from the original Premium Sound option). Premium Sound option from Ford offered better than normal speakers with a mini amp from the factory (stock amp was junk, but Prem.Sound speakers are way better than I originally thought). But with 40 watts RMS to each speaker, those stock Ford speakers have been workin just fine, and sound clean still for over 4 years in my Contour. So, the way I figure, if you had the premium Sound option before, then all you'd need is a single 5 channel amp, and you could even add another sub (even if you already have one), as the 5 channel amps will power a sub channel with 120 watts as well! But with the separate amp, you'll get your temp down inside your deck, which means the CD player is less lkely to skip and malfunction. Also, when amps (ie inside deck) get real hot, they don't play as clean of sound. They tend to distort more and have a higher noise to signal ratio.