Preouts.. underrated? How much voltage do you need?
That's what your gain control is for... to match the amp's input, to the voltage being supplied into them. That's singularly it's purpose, and it's got a broad range of adjustment - usually to well below 1v.
Unless you have a noise issue in your car, I'd really not even consider this as a factor - it doesn't affect anything related to sound quality, or sound in general.
I'd go with the Alpine, I've got two Alpine 7894's, and I love them.
Last year's IASCA rookie SQ competion world finals champion had that HU in his car (really, a more entry level deck in Alpine's line 2 years ago), and continues to use it this year, and is again going to world finals - this time as an advanced competitor.
If Pioneer has time alignment adjustability built into it as the Alpine decks do, then I'd consider that one also.
The JVC I don't know about their long term reliability, or SQ... but they've been making head units forever. Also, I think nearly everything they make has MP3 built into it. The shop I'm working with sells JVC HU's, and we've got one model that's $160 (marked price) that has MP3 capabilities.
Pioneer also has several lines below the 7600MP that do MP3.
Ordered a Kenwood Excelon KDC-X579. 
Linear Mode
