Sound Stage and Imaging

And the Celestion was a wild idea, I own the 5s and love them and heard the SL6s and they please me like very few speakers do, it's very personal, may not work for you

JBL has speakers in that price range. They bang for the buck with Dynamics, kick. Might not be the most smooth in the midrange, or treble but Dynamic. It depends what you like.

We could all make recommendations till the cows come home, but you should make sure you address your room (and how it effects the sound), complimentary gear synergy, and specific speakers for your musical taste to improve on soundstage and imaging.

@kraftwerkturbo ,

I thought you were using outboard subwoofers, crossed at 50 Hz? No you do not want to mess with a speakers internals. My point is asking a driver that is handling 350 Hz to do 20 Hz caused  the driver to Doppler distort a most sensitive part of the midrange. The inflection point over which Doppler distortion is not noticeable seems to be 100 Hz in my estimation dealing with electrostatic speakers. Distortion is more noticeable with these speakers. 

@mijostyn Yes, I run one large subwoofer crossing at 50 Hz, and run the Nautilus 804 as 'small' to relieve from 50 and below duty (also relieving the receiver from the heavy lifting for that frequency range). So the Nautilus woofers only have to handle 50-350. I have found that very beneficial also with other speakers/receivers combinations after initially running the the speakers/receiver as 'full range'  only 'adding' the subwoofer for the low frequencies.