You might consider the Gallo Strada 2s, they are truly great speakers and would work quite well as a desktop monitor...
I think you'll find that midrange tough to match if it pushes your buttons. I'd stick with ATC if I were you as there's probably a good chance for disappointment with other brands especially in the midrange. From the reviews I've read it seems like the changes they've made to their speakers over the years have been pretty significant improvements across the board, so you may end up being even happier in the end. Best of luck.
Sorry about this, Cwlondon! I would investigate having the driver repaired. A return to happiness should cost a fraction of moving to a different product, one which has not all that high a probability of providing the same level of satisfaction you've long enjoyed.
Just my opinion, but I've been around hundreds of different loudspeakers. None come close to the midrange of the Quad ESL57...
Trelja, Soix and RW - thank you.
After recovering from my shock, I decided that I will probably "recycle" one from another pair I have intended to use in an office or with a television but have generally been unused or in storage.
The small ATCs have surprisingly little resale value, and for the TV, not so critical so I might even replace with a pair of the $125 Pioneers.
If you look closely, you may notice I did something I would generally find barbaric, which is to drill small holes in the bottom of the desktop pair, seal the inside and outside with rubber gaskets to bolt spikes directly to the bottom from inside the cabinet.
This way, they are decoupled but stick into the desktop, and also face up a bit for better imaging and on axis listening.
This mod has not had any audible side effects, but helps significantly for this configuration and also looks pretty cool.
For the next iteration of my desktop, I will consider the bigger ATC SCM20's or any other challengers, perhaps Harbeths.
Reviewing my threads, it seems I asked a substantially similar question before, where some proposed crossover less, single driver speakers.
They might also be worth a look for magical, low level midrange and fatigue free coherence (like the 57?)
But as stated have really enjoyed these little speakers for many years - a rare example of a component I have wanted to keep more than upgrade.
Thank you for moral and technical support and Merry Xmas to all,