How much power for Merlin VSM speakers?


I bought a pair of Merlin VSM-MMs and am driving them with a Cary SS amp. While it sounds pretty good I am thinking of switching to a tube amp. I am familiar with the usual OTL suspects most people use like the Berning and Joule. I was wondering if there is anyone out there driving these speaker with a less powerful SET amp. How powerful does the amp have to be in order to not clip? Is the speaker efficient enough and its impedence curve benign enough for low powered amps? Is 30 watts enough? Am I asking the right questions?
abrahavt
...and apparently I never read through what I write for necessary corrections :(
Eno,

After a decade and a half, I still have my VSMs mated to Cary 300 SET mono blocks in a room much like yours, except with a cathedral ceiling that hits 20 feet. Not the FW, but the Cary monos are <15 wpc SET designs that need a friendly match. FWIW, this system sounds great at the moderately loud levels I run.
The legacy continues :)
Im a new owner of Merlin after reading all the amazing reviews through out the years. 
I had the vsm se running with 300b monos at 18wpc with great results. Then tried with leak 50 el34 25 wpc and the base definitely was deeper. 
Now I have them playing with a DejaVu set 2a3 3.5wpc and i lost a bit of base but gain a lot of the benefits of the amps design liquidity and that low power finesse. Im going to live with the 3.5wpc for now as me listening levels are not high. 
Wow, you must listen at very low volumes! I used 845 SET amps with Merlin VSM-MM for years, all the volume, micro and macro dynamics, transient performance one could want. But a 2a3? I had 2a3 monoblocks at the same time powering small bedroom system, tried them with Merlins, certainly didn't work for me, no bass as you mentioned. 91db speakers are definitely not meant for 2a3, 100db and above is. I doubt you'll find the 2a3 works in long run, the novelty is working on you at present.