Good monitor speakers for 300B amps.

Do you  think I can power the ProAc's with a 300B amp.

Did you read my last post? It still applies :) The correct answer is 'no' unless you in a small situation, like a desktop.

@soundrealaudioI     i can explain my philosophy which i used before
with Bache Audio -002
You have 8 watt tube power. Ok , No more,  you have to use this Revenue 8  to power midrange  and tweeter.  No more power to get 
good sound , just 8 watts, From 700hz and up to 20000, you need
high sensitivity wideband driver and tweeter.  External   subwoofer 
does not good in this situation . you need extra  midwoofer 5-6"  but you 
cannot find midbass with sensitivity more 90db.  So we used active buld 
in small amps with crossover point 700hz.  But dont worry , is not important , it will be driven just midbass, it not will be affected to tube sound

Atmasphere

I did read your post. Was I suppose to venerate it?

I remember driving a pair of Merlin floor standers with 8 watt 300 B. I don't think it is all that difficult. 

Audio Note AN-K

Yeah I was just looking at them. I have only heard them located in the corners and that model did not impress me. Are you AN-K's on stands? close to rear wall?