I'm gonna say 30 wpc should drive the Dyn's. BUT at what levels?
86db is as much the issue as is the impedance here.
I'd say look to more than 30wpc on those particular speakers. Like 60 or 80wpc.
I ran a pair of phase tech 2 ways, with 85db, 8ohm, with a BAT vk 60 with no problems. The 8ohm load helped a lot I'm sure.
Will 30wpc tube amps work? I'd say so... but how well is another story I believe.
Without trying first and buying in the blind so to speak? I'd say shoot for more power right off.
Or really, really good quality tube ints with great output Trannys. IMO.