Aftermarket headunit is definitely the way to go. I cant believe youre even tossing it up after posting up all these expensive speakers. Install a good deck first, and then worry about an amp and speakers. Also if you turn the treble all the way up on your stock unit, it will sound much better.
Both will sound great. Just go with the Unity or whatever the one between them is. Anything HAT will sound amazing, the Clarus set is one of the best out there tho.what about the claris versions? Or will the imagine be good enough?