the alpine PDX is nice in that it is compact, and takes the balanced inputs, but im not sure exactly how you run the factory wires in. usually there is a plactic adapter that you crimp your car's wires to and then plug in to the amp. this seems like a nice feature, but in reality, Line output converters like the one i use can be found for as little as $20. as for the non used wires, i simply taped the ends off and left them there in case i wanted to install the stock setup again.
i'm also gonna piggyback on your thread. im thinking about upgrading my setup as well. i have a 4X70w amp running fronts and a 10inch sub, and the sub leaves a bit to be desired, but the biggest issue is the fronts, i have alpine R 5.25inch. there is almost no midbass and the tweeter is way too bright even at the -9Db setting. simply turning the treble down on the deck just make the sound bad. i am reluctant to push 800w to my 10 inch sub as i don't care for earth shaking bass, i just want a more full and natural sound. this sub in my old Saab hit very hard at only 200w. i am planning on mounting 6.5 inch components to the door frame, as the stock mounting setup stinks. i think the bigger woofer and better install location might take care of a lot of the bass problems and soundstage problems i have. i just don't know what to get. i want good midbass and accurate sound, and smooth highs. can't spend a ton of money. i'm looking to spend $120-$180 TOPS on ebay(had great luck with great prices) for a set. its a bonus if they will also fit in the rear as i plan to replace the rear components later this summer. i have seen some diamond d362 cheap. and some focal access series. people seem to be high on them. any other suggestions?
(note: m3 gumby, i plan on upgrading to 300 or 400 watts on my 10. i think that should by plenty, especially with well installed quality components.)