The most sophisticated of all that stuff was the F#1Status PROCESSOR due to the time-domain EQ built in. I forget what it was called, but it could actually improve phase problems and improve the sound that way. The D/A conversion for that product series was second to none, at least on a measured basis.
What are you looking for? What kind of vehicle? What's your budget? What kinds of music do you listen to, and how loud?
--> What sort of SYSTEM do you have in mind to build?
That may influence the answer for your particular case.
Comments I saw were positive except the price and some don't like the controls because they simplified the face so much. I have the similar 880PRS, the 99 has four sets of outputs instead of three and a 31 band EQ over my 16 band. Seems like a lot for a bigger chip inside, but that is the way it goes. It is all DSP processing far as I know, I doubt there is an issue with sound quality. All channels have TA and the EQ is separate left and right if I recall correctly just like mine is. Mine sounds great long as you don't blow the pico fuse, but on tones it will get funky if you crank the EQ up over 3dB....but you don't seem to hear it on music. So I'm trying to change my system to minimize EQ, it started out I just tossed in what I had laying around but this is something I would do anyway. The real advantage is it being an all in one unit with no outboard processors or double DIN/etc other stuff to mount or fiddle with. You do have to get into menus for all of it but its not that hard. I still would rather an analog simplified EQ/levels because I can change them without even looking at them on the road, but what do you do. You can leave it on one setting like EQ or sub level and two clicks you are into that setting.