Of course it depends on use case. For my own studio though, not overkill at all.
As someone else pointed out, it's not that you *necessarily* need that extra SPL across the whole spectrum for a film, but if you listen loud, I would think in the bottom few octaves that extra headroom could be useful (at something like a 4m listening distance) over and above a smaller speaker. Especially if, like me, you like to run your LCR without bass management. (I know, I know..... I just like it, OK? ) If you're using BM then maybe not so much?
However, regarding reference level: I'd like to point out that in my opinion there's pretty much no such thing as reference level outside of the theatrical exhibition world any more. As a result of modern loudness specifications imposed by most distribution chains for home entertainment, the "ideal" monitoring level ends up probably needing about 3 - 6dB less than the 105dBC peak (or more like 108 with overs) required for theatrical. Of course people can crank it up if they like, but I find the dialog quite a bit hot on a home ent mix if the peak levels are up at 105!
Anyway, as a studio monitor, working at reference on content that's still in it's raw "cinema" dynamic (but in a small room at a 3m listening distance) I would definitely appreciate the SPL handling from 40 to 150Hz at least, which is where I always end up running in to active monitor limiters (or in the old days, blowing bass drivers). JBL 708 and KH310 being examples of popular speakers I know are highly possible to get sounding stressed for theatrical work, beyond about 2m listening distance. I say "highly possible" maybe that's a bit strong, but if you're doing an "aliens come down and blow up the world" type film, then definitely yes, at LF.
For what it's worth, as it happens I recently heard one of my mixes on 8361s, and they coped well with the SPL being thrown at them. Obviously rooms differ a bit in terms of power requirement, so I can't say any other speaker definitely would or wouldn't have coped, but I was a little bit surprised at how little they broke up. Otherwise they were kinda unremarkable to my ears, but these days (good monitors, good room treatment, good room correction) all rooms seem a bit unremarkable to me, so I'm probably saying that as a positive!? In the sense that I don't walk away thinking anything stands out "oh there was more clarity" or "oh that was bassy" And that's probably good as to my mind it's likely an indication that we're pretty much solving the old circle of confusion. (Of course, I think mixer preference based on the past carnage will actually take longer to settle down than the technology improvements!)