I need help with an amp decision

VanAlstine SET 400 would be a great match.

I think First Watt is a great choice but don’t think they have balanced inputs.  There’s a McCormack DNA-125 on US AudioMart for $929 that’d also be great and can be sent to SMcAudio for further upgrades if desired, but that too has only single-ended inputs.  TMR has a Parasound A21 here, but I think they also have an A21+ for $2399 if you can stretch.  Personally I’d forgo the balanced inputs and go with First Watt or McCormack, but that’s me.  Best of luck. 

@soix

@rocray corrected us, the new-ish j2 is the rare first watt amp with xlr inputs... 25 wpc single ended in 8 ohms, 13 wpc in 4

might be a good match for op’s tannoys

https://www.moon-audio.com/first-watt-j2-power-amplifier.html?gclid=Cj0KCQjw0emHBhC1ARIsAL1QGNenB0E_...

I wouldn’t be happy with just 25 Watts @ 91 dB/Watt in OP’s relatively large room, but I do like to play loud. I’ve had 93dB Tannoys and upgraded from 25 - 35 Watts to 70 and then 100, and it was notable each time. This will depend on listening habits, but it’s something for OP to keep in mind. Yeah, I know 1 Watt can be "hella loud". It can also be completely inadequate at other times.

I've seen Tannoy lovers with Pass labs amps so it must be a good match, but usually they're using the higher powered models. Again, depending on budget, I think a Parasound Halo A21 or A21+ could be a good way to go here.

With the FW offerings, it’s probably not a good choice if you like to take a dive in the mosh pit.  I don’t listen very loud usually,but when I do,the J2,and my F5 give me all I need. But there are folks that would say my version of loud,is their version of elevator music.