clarion proaudio.
specifically the dxz845mc w/ built in hard drive, and other nice features.
or the dxz745mp w/ dual 24 bit dac's and 4 volt preamp outputs - AWESOME sound qulaity.
both are the same price on ebay ($280 give or take + shipping), i am not sure in store, but they retail for $600.
i have the 845 and am switching to the 745 because i want the sound quality. the 845 sounds great, but it only has 1.8 volt outputs, so its a weak signal for the amplifiers. if you just plan on installing it, and not upgrading your spekers or amplifiers, the 845 is fine if you want the hard drive, but otherwise i'd go with the 745.
these are heavy units, meaning that they are built with good parts. i havent tried clarions amps or subs/speakers for a while...but their hu's are competing severely with Nakamichi and some of the other noble HU manufacturers in SQ, features, and overall build and quality. i traded in a Nak cd400 for this unit, and i am not at all dissaointed.
btw, they match perfectly in the 3 series.