I'm about to make a lot of people mad. The only reason I'm even posting here is that I've had Vandersteen's as well and did a direct comparison. I was always curious about Magnepan so I went out and bought a pair of 1.7's and had them for about a year. During that time, I moved them in and out of my main system that has a pair of Vandersteen Model 2's. I really didn't know what to expect. The only thing I can tell you is that after a lot of listening, I couldn't come up with 1 thing that the 1.7's did better than the 2's. They weren't bad speakers, they were just outclassed by the 2's.
What I liked about the speaker the most was the bass. I thought it was excellent compared to most other speakers in this price range. It was very realistic and musical, not like that one note theatre sound that most speakers produce. The highs are what really turned me off. There was just too much sibilance. Also, the ribbon/tweeter covered most, if not all of the mids. I just didn't find that setup very natural sounding.
As far as driving the speakers goes, I didn't think they were too bad. You don't want to use a pair of SE triods, but as long as you don't need to play them too loud, in your 20x18 room, you shouldn't have too much trouble.
I know A LOT of people like the 1.7's. I think thats great. I've no problem with that whatsoever. My opinion is just my opinion, and nothing more. I'm not trying to put Magnepan down in any way.