Hello
I agree,use the Ongaku with a good fast preamp and be prepared to a completely different experience.This wakes up the amp.I used my Ongaku with relative normal efficiency speaker 90db and rated 8 ohm and it was more than enough,but it all relative,all depends how big your room is ,how load you listen.
Yes,Ongaku are very expensive,but I would never sell mine,even if I hardly use it anymore.The rated 27 watts is very very optimistic,on a very good day 19 watts,that is at 3% thd.The output stage could give you maybe 24 watts but the driver stage just can’t provide the power to drive the grids deep into class A2( grid positive). A single 5687 as a cathode follower is way too small for that.
It is more important too look at a stabe impedance than pure sensitivity,Great would be 92-95 db with very stable impedance,not lower than 6 ohms and no difficult electrical phase angles.
please remember,the watts of a single ended tube amp always sound much morepowerful.I am now running a 48 watt,single ended 212 amp,that I build myself.It sound way stronger and powerful than my Accuphase A250 class A monoblocks .Also never underestimate,if you got very little noise at 90db on normal speakers with 95 db speakers that noise is very disturbing.That is why I use DC on my heaters On my 212 amp.I am also looking for high sensitivity speakers,but also don’t want to spend too much but also I don’t want them to be as big as a removal truck .
I is very difficult nowadays to listen to the right speakers, many people are just very reluctant since Corona.
keep us informed,will be very interesting