User "ummgood" already wrote a good review on this head unit. I am just going to add to his review.

The 9835 is Alpine's top of the line CD/MP3 receiver, excluding the esoteric F#1 and the DVD units. I previously owned several head units: an Alpine 7840, Pioneer 7400MP, Alpine 9807, and an Alpine 9811. The 9835 I have now is by far the best head unit I have owned. It sounds much better than the Alpine 9811 I had before. The treble has an amazing level of detail and "airiness." For instance, cymbal crashes sound very real and you can hear its "decay" very clearly. I did not hear this level of detail in the 9811. The bass output also appears more robust. I ran both the 9811 and 9835 with external amps and with the equalizer set to "flat," so the differences can not be attributed to the internal amps and equalizer settings. This seems to imply that the 9835 has a better quality pre-amp output or digital analog convertor (DAC). The Bass Engine Pro of the 9835 allows greater control in setting the crossover points and slope than the Bass Engine Plus of the 9811. I got the 9835 on eBay for $405 shipped. My system also consists of JL Audio XR-525CSi component speakers, an Image Dynamics IDQ-10 subwoofer, and MTX 342 and 2100x amps in a Ford Ranger regular cab pickup.

It's amazing what you can adjust on this head unit. It will be too much to write down all you can do.
To me, the two most useful features of the 9835 are time correction and the adjustable crossover. The time correction feature allows you to delay the output of the speaker closest to you (in millisecond increments!). The result of this adjustment is that the "imaging" is much more clear, that is "voices" seem to come from distinct locations in front of you. The crossover is highly adjustable with alot of points to choose from and you can even adjust it's slope (from -6dB to -24dB). These fine adjustments allows for the optimal blending of the output of the sub and main speakers. The 9835 also has a 5 band equalizer which I did not feel the need to use since the sound I am getting is already good.

It is important to mention that the 9835 is a very feature laden head unit intended for use by experienced car audio enthusiasts. If you are a novice to car audio and are looking for a simple basic CD player, then this head unit will be too much for you. I found the controls a little tedious at first, but once I became familiar with it, it was rather easy. I actually was able to figure out most of the controls and made nearly all the adjustments without even reading the manual. YMMV.

Here is a detailed, well-written review on another site which favors the Alpine 9835 to a similar priced Pioneer 860MP head unit...
http://forum.sounddomain.com/forum/ultimatebb.cgi?ubb=get_topic;f=8;t=014102

For those novices out there, here are a couple of great sites which explain, in layman's terms, the basic principles of car audio...
http://www.caraudiohelp.com
http://www.crutchfieldadvisor.com/S-ZbW0HlXH2Yj/learningcenter/car/?listAll=1