separate amp for mids and tweeters with an active crossover that is easily accessible for level adjustments and crossover tweaks.
tweeters are easily ran 2 ohm stereo (two 4 ohm tweeters per channel) from most 2 channel amps ever made.
mids are easily ran 1 ohm stereo (four 4 ohm mids per channel). these amps are less common, but many are available.
you won't need much power for the tweeters, and most amps capable of 1 ohm stereo can produce decent power.
there are hundreds of amps that can do what you want, what's your budget for two amps?