So I see where a lot of people pair Marantz with Emotiva Amps. Then why would this not be an obvious problem. Unless the majority of people all use unbalanced connections
Those who use Marantz AVRs, or Denon's obviously with the XPA gen3 are likely the majority so they would have no issues and those using the Marantz AVP may not all use XLR, I would guess 50/50, so you will see why most users won't have this issue.
A quick search found that those who use similar combinations do have the same issues. There must be more if you search harder:
Marantz AV7702 MKII to XPA-7. Input Gains. | The Emotiva Lounge (proboards.com)
I would agree with TLSGuy partially that it is an Emotiva issue, only partially because they haven't really done anything wrong except they should have provided some flexibility, if not variable, at least something like a selector switch (hi/lo selection).
The main reason for such kind of issue has more to do with your speaker's sensitivity and your seating distance. The BP7001's sensitivity was listed 92 dB (that's vague without stating /w or /2.83V, anechoic or in room) but it could well be 95 dB or more in your room, and the way you connect them as they have powered subs.
So to be fair, the Emotiva is not to blame, strictly speaking. As
@lovinthehd alluded to earlier, you do have another simple solution if you want to go back to XLRs, by using a spl meter and adjust all channels to the same level. I don't like that simple solution because then you have to record what you have adjusted to each channel and allow for that in your head when you adjust the volume dial. That may not be an issue for most people who just do it once and are happy to forget and enjoy. It is for me, as I do enjoy playing around with REW and the Audyssey Editor App.
You cannot do such manual adjustment and the re-run Audyssey, or more precisely, you can, but then Audyssey would set all channels back to -12.
Consider yourself lucky too, that switching to RCA is enough to do the trick, if you had certain Klipsch models, RCA outputs lower voltage may not be low enough.