having an amp strictly for your tweeters isn't anything out of the ordinary.
you don't need a very big amp though.
i used to run a set of boston components bi-amped and active.
i had a 160 watt amp going to the woofers/mids and a 100 watt amp going to the tweeters.
lots of headroom available in the setup and i had a lot of flexibility for tuning.