Brian, my issue is not so much on sitting a crazy distance back from ribbons in a 48' deep room.
It would be possible to have Apogees 3' from front wall, me at rear wall, thus sitting 43-44' from them.
Not a formula for success.
I actually sit 12-13' from my Zus, and find that works, w the spkrs 8' from front wall, and rear wall 15' behind me.
No my enquiry is whether I sit 9' from them as you do, or 12-13', or further, don't we still have the persistent issue of fully energizing that large volume.
I can't see the question of sitting near field or further away having any bearing on the need to saturate a large volume of air, w bass extension to match.
And hence the age old question of tubes v SS.
Now if you've designed a hybrid amp which grabs the Apogees and gets them to fess up in such a volume, with a good tube sensibility, and laughs at Apogee current demands and low impedance demands and low sensitivity, this would have to be of interest to the potential Apogee owner wanting total performance.
I do know Henk in NL strongly recommends a modded version of a two decades old Krell design.
But a current day equivalent w the advantage of a tube signature is more my thing.