Hi Rob!
.......... The hassle though is the difficulty of trying before you buy and there really isn’t a way for me to try a K812 whichis something I would really like to do.
...........
As for the Elegia, were you able to purchase it new? Is It still available? I have never heard a Focal headphone so can you please say a few words regarding its dynamics compared to the K872?
Also, you mentioned you own a studio. May I ask what kind of production do you do and if you do it to make a living or as an amateur?
Cheers,
Antun
Hi Antun
I'll try not to get too long winded.....

Yes try before you buy is always is always ideal but problematic, especially today...luckily I was able to borrow a pair of K812s for a few weeks, but that was just after I picked up my HD800S in 2016...I was expecting the worst but came away wishing I had gotten the AKGs instead.

So I had a relatively good idea what to expect with the K872.
Depending on where you are located Amazon UK currently have the K812 for a reasonable price, and as they can ship to Canada without VAT I've been tempted.
But even though I really like them is not any indication they have global acceptance ... YMMV ... lol
Focal, relatively speaking, are new to the headphone world, starting in 2012, AKG started with headphones in 1949 and Sennheiser 1972 and both have a long history of diaphragm development for microphones prior to doing their headsets, so basically a new kid on the block. I did manage to audition the Utopia but for their asking price was not overly impressed and preferred the HD800S and the K812s for that matter.
Recently wanting a second closed back to compliment the K872s the Elegia was a curiosity and I was able to pick them up locally from a gentleman who gave them literally an hour of use as he preferred his IEMs, so basically new, they were a silly price so thought I'd give them a go.
Initially I agreed with his impressions and had a bit of buyer's remorse but after a few days the phones really did change (controversial of course), opened up completely, lost their edginess and the sound-stage improved, even Focal state in their manual a minimal 24 hr break-in.
For a closed phone they are completely different from the AKG K872, more akin to having 2 speakers placed on either side of the head, which they are, compared to their other phones Focal did some revisions to the driver and cup but the AKG IMHO are a much more sophisticated endeavour and sound more opened backed than closed. Oddly, Focal remind me of my past Grados even though design wise they are totally different. Both phones are relatively dynamic but the Elegia are more up front, the AKG can step back but show their presence when needed.
The Elegia has been discontinued and replaced by the Celestee but are still widely available and for about 1/2 or less their original pricing.
To be honest though.. I'm a bit out of the headphone loop, and probably an old stick in the mud with my AKGs and Sennheisers...brand loyalty brand and all that, I'm happy with them but there are quite a few new offerings out there..still undecided with Focal as they have stiff competition with the much more affordable Sennheiser HD600 series, the closed back Elegia is the odd man out.
As for studio work, starting doing tape manipulation, Music Concrete prior to going to University in the early 70s and later I had my own small electronic music studio as an Electro-Acoustic music composer. Did some on-site recording for small jazz and performance groups, so not really commercial work.
Should note, got my first Bryston 2BLP back then to power my studio monitors...and the 2BLP pro prior to the BHA-1 also did a great job of bringing the K240DF (my first AKG 1977) and K501's headphones to life..... way back when.
...as for your K135s...always fun acquiring old new stock of something.