Input on speaker sizing for a lively room.

My listening area is a 34x22x8 open floor area of our home. It is comprised of both a great room and the kitchen/dining area. Flooring is hardwood with typical rugs where appropriate as well as having some large windows. My listening is two channel audio only and often while casually doing daily routines with the family.

My system has evolved to a point where I feel a plateau has been reached. Listed as fallow:

Herron M1A mono amps
Herron VTSP-1A-166 pre
Arcam CD23T CDP
Morrows Mid level cabling
Dunlavy Cantata

My current speakers are Dunlavy Cantata's located on the interior long wall. These speakers perform quite nicely at mid level volume. Where I would like improvement is both at low volume listening and some shear gusto above mid volume with a smooth top end. I realize the Cantata's are being unfairly critiqued here as they certainly are out of their design element.

Some personal speaker criteria. While my listening area is large, I would prefer to stay with a slightly undersize full range floor stander speaker for WAF. We have a quitar and piano player in the family so those traits are strongly admired. My budget would be 15K. A few speakers I have on a short for a demo are as fallows:

Silverline Boleros
Vandersteen Quatro
Verity Sarastro

General comments: Everything I read about Silverline sounds like utopia. Having talked with Alan Yun several times, his passion is inspiring. I have listened to the Vandy's briefly in a studio as they are local. It was that event that made me stop and decide to take my time with this decision. I could listen more if the sound was acceptable to more attuned ears in the household...

Feel free to offer up any input. Like many, I am at an age where this opportunity won't likely be repeated and would like explore possibilities I likely would never have known about. Thank you