Hi Matt,
I have no experience with Dynaudio speakers, but my instinct would be to proceed with caution before going to tube amplification with them. In addition to the comments by Ralph and Mapman just above, I would emphasize that high quality high powered tube amplification tends to be quite expensive. And you clearly need lots of watts.
Based on the impedance curve of your speakers, shown in Stereophile's review
here, I would consider their 86 db/2.83V/1m sensitivity to be roughly equivalent to 84 db/1Watt/1m. At typical listening distances (say 10 to 12 feet or so) that would mean that 70 watts into both speakers would produce a maximum SPL of around 96 db or so. While that is adequate for most listeners when listening to highly compressed rock music, I suspect it would be very disappointing with a lot of material having wide dynamic range (i.e., a wide difference in volume between the loudest and the softest notes).
My listening is about 90% classical (including a lot of wide dynamic range symphonic material), 5% rock, and 5% miscellaneous. I've measured some of the classical material I listen to as reaching 105 db at my listening position, which my 98 db/1W/1m speakers and 70W amp handle comfortably.
Although I haven't heard them, if you do want to consider tube amplification you may want to look into the higher powered models from Rogue Audio. Some of them provide close to 200 watts, at relatively reasonable prices, and seem to receive generally favorable user comments.
Best regards,
-- Al