"...in the same search mode and owning the original Boxers myself."
r-man: still researching. List narrowed to Fritz, Salk and the odd pre-own 'bigger-name'. I was way wrong on room dimensions in the OP: actually ˜2500cf w/ high ceilings so that opens the field a bit, so to speak. I too really like the Boxers v1's - they'll be moved to master bedroom and paired with single REL R-328 sub.
A question I keep coming back to: within my spec will whatever replaces the Boxer be significantly 'better'? It's a rhetorical question.
"...Osborn Eos Reference Elite"
jtgof: these are intriguing. If price on their website is AUD it works out to under $2800 USD. Of course, availability anbd/or ship-to in USA is a question as is warranty service should anything go wrong. <= probly low likelihood.