Think there was a brass version Avant, finding one might not be easy though - yes, its showing in the modern section part of the B&O site.
I do have 4K in the Avant MK 1, using Netflix and Amazon Prime (Fire TV box) - it's not HDR of course, so the step up in PQ is noticeable, it can look excellent, but its nothing like the more drastic eye popping imagery you get with the newer all HDR TV's. As everyone will tell you, its the HDR bit of new TV's that has moved things on PQ wise.
But in the end, for me the HDR part wasn't that important, hence i went for the Avant Mk 1 (I'm into older movies, where 4K HDR isn't relevant. One day when Sky Sports is all in 4K and not so expensive, but until then....)..so i'll likely revisit getting some HDR on board in 3-5 years time. They will likely be more B&O HDR choices in a few years, and maybe even with some B&O sheen on the UI.
Anyway, it was much more important to keep the UI and functionality as it is on my 12-65 (an option no? - 4K aside, a much better TV than the Avant) - got the same UI on both TV's, couldn't be happier. A simple problem free life has its merits, and the ex-display Avant was cheaper than a new TV.
I, like you, could have swapped my 14 for an 11. There was no great reason for going for the Avant over the 11, it was more a nod to getting something a bit more up to date, that and my brain not functioning properly. So i miss the 11 design, but the Avant is sleek enough - beware the speaker can make a bit of a noise when it pops back in - touch odd, but no deal breaker for me. And not quiet as flush to the wall as the 11, but again no biggie for me.
Mine is fed by a matrix to one HDMI input on the Avant - cant quite remember, but it might be that only one of the HDMI ports is HDMI 2.0 (i.e. 4K decoding), but i only needed one, so no big deal. The sound on the Avant is excellent.
Enough rambling from me - either 11 or Avant Mk 1, you'll be happy with.