I agree, the Alpine units were (are) a good choice in the 1.5 din size. The only drawback is that they do not have satellite radio capability built in, like the newer Pioneer, etc. do. Too bad Alpine got out of the 1.5 din market.
The CDA-D852 and (newer) CDA-D853 are the lower end units, while still more than adequate.
The CDA-D855 and (newer) CDA-D857 are the high-end units, and feature 4 volt preouts (better signal to noise), and I believe a better processer. (You *are* going to use an external amplifier, right?)
All models do have internal amplifiers, but I would not use the internal amp.
On ebay right now there are two D857 units; one has a "buy it now" of almost $500.00. That seems a little high to me.
I bought a used D855 on ebay, somewhere in the $250 range if I recall.
Also, parts are still available for these head units. The front face frequently has broken corners on used units; I had to replace mine when I bought it(picture on ebay showed a perfect unit, but it arrived broken, and the seller refused to refund or pay for the damage...).
I also picked up a used a/d/s PQ20 amp I plan to install as well (too many projects). The old a/d/s PQ20 (4 channel @ 80 watts per) and PH15 (6 channel @ 55 watts per) are some of the best amplifiers (in an affordable range) ever made for car stereo. They still trade on ebay, and go in the $200 to $350 used.
I've got a PH15 in our '92 Jeep Cherokee, its a wonderful amplifier [img]smile.gif[/img]
I like old, well built audio - I have 3 sets of Dahlquist speakers in the house (M905, M907, and M909).
Anyway, good luck.