Lots of sage advice so far. For whatever MY experience is worth (granted, probably not much due to our systems and ears being quite different), I have an A-21 amp driving a pair of old Thiel 3.6s. I had a used SP-17 on demo at home for a while and absolutely would have bought it if the dealer's price would have been more reasonable. I ended up with an SP-16, which I like a lot, but the SP-17 was a bit more open and refined sounding. The remote volume control was more sensitive than the SP-16's too.
Good luck with your search.
Good luck with your search.