SET suggestions up to $3k (used)

Don't know the size of your listening room or your preferred listening level. I'm thinking you're on the right track in thinking 8 watts. I drive 93dB efficient JBL monitors with my ~7 watts of SET 300B power and really enjoy it.

I think you're in a target-rich environment, though shopping might take some patience. Just keep checking all the various audio sales websites. The equipment is out there.

How about considering a solid state class A integrated such as the Sugden A21se? It can be had for $3250. It is 30 watts of pure class A, single ended. Unless of course your heart is set on tubes. The Sugden has a similar sound to a tube Amp, without the hassle of tubes.

Maybe a used Line Magnetic with more power.

I use a 4 watt Deware Mini Torii with my 92db Ref 3A de Capos

plenty loud in a 22x12 open room

I'd second the Coincident, my two pieces very nice. Whatever amp you purchase add boutique tubes to budget if not included in sale. You'll never hear full potential of 300B amp with second rate tubes.