Have you considered Dynaudio Contour 3.4's? They are in the same price range (used) as the Nautilus and have excellent bottom end, with great depth and transparency. The Excite 36's have exceptional bottom end and you can pickup a new pair for >$2500. You also might consider Focal Electra's (not the BE, they're a little out of budget). I own Dyn's for my hometheater and the 82's sound just as full in stereo as they do in 2.1 mode (the 82's are similar in specs as the Excite 36). I have heard most of the speakers on your list along with the X-5 and they are all fantastic speakers.
I have a 7.1 system with Cambridge audio Azur 640R, Dyn 82 front, 52 sides and 122c with an Earthquake supernova sub.
I have a 7.1 system with Cambridge audio Azur 640R, Dyn 82 front, 52 sides and 122c with an Earthquake supernova sub.