The SET amp question.

At 110 dB, unless you have a huge room to fill to orchestral live levels, you have the entire universe of SE designs to try. From the 2-3 watt 2A3 based to 9-10 wpc 300bs on up to the 50 wpc Kronzillas. Lots of great amps to try in that range.
Tell us your room size, music type, volume level and budget and we can make recommendations.

Well that's a pretty good size space but 102 dB is pretty darn efficient. Its not quite double the size of my room (14 x 23) but I do have 8.5' ceilings. Assumming you've got 7.5' its less than 50% larger, but lets consider it twice as large for now. I found 9wpc 300b amps fine for moderate volume singer songwriter, soft rock, acoustic jazz stuff but the amps ran out of steam with more heavily layered material at somewhat higher volumes; with 89 dB Merlins (flat 6 ohm impedance). IIRC, each 3 dB increase in sensitivity is equivalent to doubling the power. So 89-92-95-98-101 That's about 16x more effective power, so the 300bs should be just fine and maybe even the 2A3s. There are lots of 300b amps out there and the cost of decent power tubes has dropped.