Upgrade on new internals. Suggestions?

Morel speakers kill, in my opinion.  I use their tweeters in almost all my home theatre designs.  Their car audio stuff is really nice, if a bit pricey.  If you want accuracy and high power handling, Morel is near the top of the heap.  Phoenix Gold Elite systems use Morel speakers.

Which can get annoying sometimes, my friend!

The above can be true for a beginner or someone who really doesn't know what they're doing.  But for a person experienced in loudspeaker design, the oposite is true and makes up the most fun part of the process.  Using multiple drivers solves way more problems than it creates, as you can "cover" for resonances and poor response bands (every speaker has these) by properly designing the crossover and handing off to a driver better able to handle the troublesome band, and by taking advantage of multiple drivers in the same band increasing efficiency in that band.  Easier than using multiple notch filters and pads.  And if someone building a system does not understand how to deal with differing sensitivities, phase changes, impedence, lobing, or acoustic time alignment, then that person should not be designing the crossover.  This is my experience and my opinion, and there are those who will disagree, especially the advocates of the mythical "single-full-range-driver."  I have yet to hear one that I can accept as "hi fi," however.

As to horns in general, I think they sound great in a long-throw outdoor sound reinforcement system.  I hate them for stereo (yes even Klipsch) and I especially think they are the wrong solution in a car.  But again, that's just my opinion.