Avantgarde Duos - right for me?

I just wanted some opinions on the Avantgarde Duos as an upgrade path for my system.

My system currently consists of Manley 300b monoblocks, Manley Shrimp preamp, Acoustic Zen speaker and interconnect cabling and Omega Superhemp single driver speakers.

Overall I have been pleased with this system and just love the strengths of an SET/single driver system. Very intimate, great speed and tone, fabulous midrange, etc.

What the system is unfortunately lacking still is big dynamics and deep bass. I have read good things about the Avantgarge Duos but I cant find a local place to audition these speakers first hand. At any rate, I would certainly be looking to buy these pricey speakers used on Agon.

Any opinions on how the Duos would sound with the Manley 300b monoblocks? How small is the "sweet spot" on the Duos? I ask this because I do a lot of entertaining and would ideally like a speaker that has a decent sized listening area. What sized room do the Duos need to sound right? My living room is 18x24. Are there any other high sensitivity speakers that would be better than the Duos?