Living Voice are built for valves, sorry tubes and have a benign and flat impedence. I asked Kevin scott who builds them and he said they are built for tube amps, but not flea powered ones. If your favour jazz combos or solo singers, 8 watts will do, 18+ if its Mahler or heavy rock. So 15 watts as you describe, will be in the ballpark. I use a 22watt SET and it is perfect, but high powered SETs are expensive. As you say Art Audio, audio note would be good, the Leben amps are lovely, but the one I heard, a bit base light. If it was me, a VAC Avatar 2nd hand, if I really felt I deserve a present, a Vac Phi betta. I don't think I deserve a present by the way.
Valve Amplifier suited for my system
I own Living Voice IBR-X speakers of 94db sensitivity,Resolution Audio Opus 21 CD plaver my system sounds very good,I wish to buy tube amp with a minimum output of 15watts per channel,I like resolving delicate and lush sound which amp from Shindo,Wavac,Art Audio,Leben,Almarro, and Audio Note or any other make will match with my system