I use the midrange and tweeter from this set and am quite happy with them. The 8.9 is a great dedicated midrange to use between 250-5000Hz or so and the tweeter is very nice and smooth, yet still highly detailed.
Compared to Mark's previous offerings, the Euphoria 8.9 is the most efficient by a fairly good margin and will play the lowest, but it is not a fullrange driver - you will need a tweeter up top. I'm not going to list of bunch of fru-fru SQ adjectives, but basically it is a highly capable midrange, especially for its size.
The tweeter is small enough to fit most anywhere and you'd never complain about harshness. It won't play as low as 1" tweeters, but it covers the top end very nicely. I have the mids crossed between 250 and 3500 and the tweeters from 4500 and up (acoustic crossover points).