Speaker shopping Help?

I've had Dali Helicon 400 MK II for a couple of months and love them. The only problem is they're a little too small for my 23ftx28ftx14ft room. I like a speaker that imaging is a high priority. They need to be rich but detailed, non fatiguing. Tight bass that goes down to at least 35hz. Here's my long list:
Wilson Sophia II
Kef Reference 205/2
Revel Ultima Studio II
Focal Electra 1037BE
Thiel 3.7
Sonus Faber Cremona

The rest of my rig is a computer music server running through a Bel Canto DAC 3 into a Spectron Musician III SE MK II. All MIT cables. thanks in advance for all opinions.
go to the dali 800 if you really love the sound. they will compete with all the above, and you won't trade for another set of sonic issues. if you don't dig the sound, expand your search.
Recommend the Focals. Could even look for a pair of used Utopias (Divas or even Altos) now that the new line is out. Really need to hear before you buy in case they are not your taste.
My experience has been that some speakers have that room filling sound and some have that more sweet spot type sound. Some "load the room" and some don't. Not sure it is a question of size. I used to sell the Reference 3A deCappo's and they really had that big sound, even though they were a monitor speaker.
"They need to be rich but detailed, non fatiguing. Tight bass that goes down to at least 35hz"

Philefreak, except for exceeding your bass frequency extension spec by 13Hz, your description seems to match my Vienna Mahlers to a T. Reason I mention them is that the Spectron Mus 3 with its very high damping factor should control Mahlers with a lot of ease, and let them yield a very extended bass that is tuneful and without any bloat in any frequency band. Treble is extended but not shrieky. They sound 'rich' in the sense of being capable of rendering harmonic complexity, but not in the sense of yielding a 'caramelized' euphonic glow to the music. . . Staging/imaging is excellent. . . but they do not yield a pinhead of a sweetspot. . . rather they are very forgiving about listening position. Mahlers work best in large rooms like yours. and mine. Only caveat is that all Vienna speakers must be set up very carefully to pressurize the room without frequency hotspots and sound their best. Some dealers like Soundings Hifi use a process designed by Sumiko called MasterSet, which works extremely well. G.
Magnepan 20.1 or a 3 series with double subs.

My room is 19 X 31 with 14 ft peak open beam ceiling

I am using 3.5Rs biamped with a SVS powered sub. THe sound stage is big, but I could use a second sub
Ohm Walsh 5 S3

great match to your spectron & room size
omnidirectional - excellent room loading
Maybe a pair of soundlab speakers would fit your bill; specs show them down to 24hz;ever owned a electrostatic speaker?
I would add the Dynaudio C4 to your short list..Full range down to 20hz.One of the best tweeters made.I owned the Focal utopias before and there is no really no comparison.The dyns just do it right especially in your room size