When you say small tube amp I'm thinking you mean low powered as I've seen 70 lb monster SET's that only make a couple of watts.
My Tang Band W8-1808 OB's and Fostex Frugal Horn Mk3 are 93 dbs and will play very loud in a 15X15 room powered by a 3.5 watt amp with headroom to spare. I often drive the Frugals with a 2.5 watt APPJ ( Miniwatt ) with equally good results. Compared to the first watt all the other watts are relatively weak.
Unless you want to rock the neighborhood 92 db speakers will put you at the threshold of triode land.
I have been sending nbumerous questions to dagogo's own Philip Holmes who is our resident tube amplifier expert getting advice on tube amplifier topologies and which he feels are the best ones for reasonable money. It really comes down to the quality of the transformers and windings and he notes that most companies don't have the expertise in the windings to really make the best sound. He noted that there are easier ones that they generally get right - EL84 based and 300b.
He seems less of a fan of the 845, 211 and other high output versions. Which may explain why I prefer the EL 84 OTO to some beefier more expensive output tube amps.
I really want to get some 300b, 2a3 and EL84 based amps in to try as well as PP amps operating in triode mode. The latter is likely better suited as a reviewing amplifier because it presents more options for powering more difficult to handle loudspeakers. I've been looking into Audio Space, Line Magnetic, and Melody mostly as AN is expensive. Then again I always get the gnawing sensation that you often gets what you pays for. Looking at the Meishu 300B makes me not want to hear it again because if I end up wanting it I will look at the bank account and be disappointed.