When I did my kitchen a few years ago I got quotes from the brands you mentioned.
Then based on the recommendation of a friend I went to see a local bespoke kitchen company.
They were utterly brilliant and the prices similar to SieMatic.
The big difference was they built all the cabinetry to order so the design wasn't compromised by standard unit sizes. It's also all solid wood (most companies make the unit carcasses from cheaper alternatives and reserve the expensive products for elements that can be seen).
Awkward spaces were transformed into useful features (a recess for a huge chopping board for example) and really practical advice like having a power socket in the tall cupboard in the utility room so I could store my dyson out of the way in there and keep it charged).
The only downside was the amount of choice I had! Literally any colour, any handle, finish, appliance, worktops etc
The design service was very personal and the fitting excellent. Nothing was too much trouble.
As a small business, word of mouth and recommendations was a big deal for them, so they went out of their way to provide excellent service.
They came back after 2 weeks to check for any snags (i didn't think I had any) but they spotted a couple of minor issues and rectified them (a draw that wasn't closing quite a smoothly as they felt it should was one).
A month later my DM was so impressed she ordered a new kitchen from them!!!
So sorry for the long post, but I'd definitely consider visiting a bespoke kitchen company. You've got the budget for it and I think it might be an eye opener about what you can get.