OEM units cost/performance ratios still suck. A typical head unit from a dealer usualy runs over 500 bux alone and are 90% of the time WAY UNDERPOWERED.
Some BOSE systems are proprietary and require addapters to operate with aftermarket equipment, as are some Harman Kardon/Infinity systems. Philps has some really good stuff in the oem market, but it falls short too.
I have worked for Harman Int. and Philips and can honestly say: Thier oem stuff isnt all that bad, but it is designed to make them money, and that's all. They make it as difficult as possible for the layman to make improvements. Thus the proprietary statement I made.

Its cheaper and less aggravating just to buy an aftermarket headunit and speakers and use exsisting wiring for your system (I run all new wiring myself). OEM amplifiers are almost guaranteed to have odd impedances and input voltages.....throw em away or sell em on ebay.

IMO, The best amps made were built before 1995. Good manufacturers are Fosgate, Dennon, Adcom, Sony and Proton. All are underrated in power and play cleaner than this new garbage.
Good luck ya'll.