I have the CDA-7998. It is a great head unit, I dont regret buying it at all. I also have the Pioneer DEH-P930 in my other car..........and thats a great HU as well. It's more flashy............but I find them both to be on par with eachother.
The Alpine does have better SQ than the Pioneer though.
If you dont want to spend all your money on the 7998.........your next best HU from Alpine to get would be the 9815...........which from my testing is the same HU as the 7998.......without the Phantom Face Feature.
Either way you'll be happy!!!!