Lawrence
I have a pair of the HempTones, the big ones, and have powered them with SET, PP, Tripath, A-Mosfet, and they ALL sound great, to my surprise, and relief. In fact, I would say if I had to choose, I would use the Hafler 250 watt sand amp, just because of the overall ...gestalt, but 2 watts is also plenty, so you can use anything, it would seem, and be very successful. The hemp cones are not at all weird about what you use for an amp, and I would bet the Naim stuff would be bullseye, with their very even tone, and buckets of current.
Both the B200 and Hemp are power speakers, and can sink ALOT of juice, no worries, especially the B200, which sounds better the louder you play it.