Upgrade from ProAc Response D2 in small room

What specific improvements are you looking for, what’s your budget, and are you looking for new or used?

I'm curious,what exactly about the sound are you trying to improve?
 Is your room properly treated?
 If the rooms Acoustics are sorted out,with those speakers,I think I would be looking at an amplifier upgrade before moving on from the ProAc's...
 

@goethe58 "treated with several GIK bass traps" how was this done and did you take any RTA alongside your listening to them in your space.

Cos I don't know what is missing that you want to change unless you just have what is called upgradeitis

@OP - If you like the Response D2, why not listen to the Response D20. I used a pair of Proac 2.5s in a room smaller than that for many years with excellent results. BTW, in a room that size you need some diffusion as well as bass trapping. I would see to that before changing speakers.

+1 on Yoyoyaya

if the sound signature of the Proac is something you like, stick to it. I heard the Proac D2 and there are very good but not for me. I settled for Falcon. you may need a bigger Proac. also, the D20R has a ribbon tweet. you may like it

what may happen is you may have no need for a sub