First, if you choose the Elevation Speakers, I would urge you consider not repurposing those to a more demanding job.
I do not know your listening habits; likewise I am not experienced with those speakers. However, I would consider those to be on par with small Standmounts, and with the sacrifices usually made for size, they just will not perform as well.
The caveat there is if you only game or use them for HT, it may very well not even matter.
I mentioned before that my primary usage is music, and I built my system out to support Multi-Channel recordings. I'm not talking running in Multi-channel stereo, but DTS 5.1 CDs and SACD content. I did not want to leave anything on the table in terms of a speaker not hanging with my mains, and just short of having 5 matching towers, I did just that.
So back to the other point... this is a rabbit hole that people tend to fall down. I was the same way early on, trying to figure out how to match EVERYTHING.
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The truth of it is that it really does not matter, and for this you need to consider what these speakers do. Unlike the Mains and the Center, the other speakers are all in a support roll. Yes, that roll has changed over the years and there are greater demands placed on them, but the fine point is that you are never going to notice a timbre mismatch when a helicopter flies overhead, or a bullet whizzes past...
Most people I've talked to also prefer a speaker that has a bit more controlled directivity to it for Atmos, as opposed to wide dispersion.
Those examples I cited are all more or less in the realm of Spacial Cues. By getting at least four good Atmos points, usually Top Front and Top Back, and having a very tightly dialed in system in terms of placement and separation of Atmos layer from Bed Layer, you then achieve a bubble of sound where you get that added dimension of sound coming from overhead.
I know several members here with very discerning demands for their front speakers who use mismatched speakers for the Surrounds. Likewise, many friends here use different speaker for Atmos (those using in-ceiling for example, rarely have the option of matching their mains).
Regardless, at the end of the day, it is your system and your ducats!
By all accounts, the SVS Elevation speakers are great for wall mounting at the ceiling and getting that near to perfect Atmos placement. I do not think you would be disappointed in using those
for that purpose.