I owned the LCD-2.2 for a year, and have the LCD-X now. This past weekend, I tried the LCD-3 again--in a direct comparison against the LCD-X. There is no such thing as lush thick mids and a large soundstage in any headphone. You have to decide what you value more.
The LCD-3 has the lushest thickest mids in the Audeze line, with good detail, but a very intimate soundstage. The LCD-3 is all about the mids. The bass is nicely defined, but takes a back seat to the mids. The LCD-3 treble is very subdued. I consider the LCD-3 the most forgiving, compared to the LCD-2 and LCD-X.
The LCD-X has the the most neutral balance of the three, and the largest soundstage by a mile. The LCD-X mids have body and substance, but don't have the lush thick character of the LCD-3. To my ears, the LCD-X easily has the most detail of the three. This may be because there's no focus on any one aspect of the signature. The LCD-X treble definition, smoothness, and coherence spanks the LCD-3 and LCD-2.
I see no reason to own an LCD-2 and LCD-X. The LCD-2 signature lies between the LCD-X and LCD-3--but with less overall detail, looser sub-bass and a bit of grain in the treble. Price aside, the LCD-X and LCD-3 would be the best complement--due to their very different signatures.
It would be insane to choose the LCD-X or LCD-3 without hearing both yourself.