Both great speakers and I have experience with both. I prefer the Dynaudios, but as a dealer some bias creeps in.
Both will require a large amount of current to get the most out of them. The Theta is a decent amp and will work just fine, though.
I prefer the top of the Dynaudio's. Bass is pretty much a wash imho, both excel in the lower frequency range. I could live with either for life, but if I had to make a decision, I would choose Dynaudio.