These HU's look quite interesting, I kind of see CD's as a bit of a waste of time when you can store so much more on MP3 and not have to waste time and money burning and buying to update your collection.
Have been out of audio for a while myself but..
The HP/LP can make a real world of difference, as it allows you to set cut of frequencies to the components so they don't get a load of stuff that they cannot handle.
I dont know if Alpine still does it, but you used to be able to set up the sound on your PC then burn the config file to a disc and install it onto the HU, that was a cool feature.
The time correction is also a very sublte but big difference to the sound, as it makes all the speakers work together so the sound hits you all at once!
In my experience, VFM wise, a good Alpine Head unit, a 1/2 decent pair of front 17cm components and a puchy 10" sub will have your car sounding, not massivly loud but super sweet

Not really relevant if you have no interest in expanding but hope that helps.