Harbeth 30.1 or 40.1

Actually, nothing wrong with the Spatial X5.  But hear the Harbeth on You tube and the midrange sound can’t get away from my head.  I know the sound quality from YouTube is not good in any way, and it depends on the gear and room condition.  But still, I know I need to try them.  The videos I saw are for 30.1.  But there is a used 40.1 for sale locally, so I am wondering.  Another consideration is the price.  The 40.1 is a double of 30.1.  I also need to buy an amp.  So, I can get the 30.1 and the amp for the price of the 40.1.  The biggest concern is, I am spending the money but can’t utilize the benefit because of the constraint of room size and listen volume.

@jond how would you describe the difference?  I never own a monitor speaker, all my speakers are full range speakers.  But then recently, I feel they are actually a bit too big for me.  I realize they sound better when I turn up the volume, but then it is too loud to my taste.  Is there such a thing as optimum listening volume for different speakers?

gte357 to me there is an optimum listening volume for each piece of music not so much for each speaker. To my ears the difference between the two is the 30.1 images a bit more precisely but the images don't have the density of the 40.1. Also you get more sense of the room the music was recorded in with the 40.1 because of their much deeper bass. The 40.1 is much deeper in the bass but a tad less airy on top. Both speakers have a top notch midrange detailed and transparent with natural warmth. 

When you say the 40.1 has much deeper bass, does it need a louder volume to bring it out?  Or they are at similar volume?

40.1 seem designed for larger rooms and yes far out from walls. 

I’d start with the smaller Harbeths in that room.

Buy used and don’t overpay or buy new with return policy if you want to keep your options open.