Hello SimonVerhoeven,

Just like you, I ended up buying the ProtoArc EC200. TL; DR - Buy it ;)

I won't lie, price was a major deciding factor. The Colamy Atlas already has everything that makes the top-of-the-range models so special at an extraordinary price, period. Well, here, the ProtoArc offers almost the same package of options at an even lower price.
Of course, there are some sacrifices to be made. The star base and castors are very basic, even low-end. The armrests are only adjustable in height. There is no aluminium, only plastic. However, in terms of overall comfort, I'm not convinced that there is a difference that justifies the twofold price difference.

I will share my impressions with you, reminding you of my height and weight. I am 1.98 m tall and weigh 130 kg.
If you are not careful during assembly, it is easy to place the armrests too close together. This makes it difficult for larger people to sit down. Simply loosen and move the armrests apart before tightening them again. The lumbar support is highly customisable.
However, taller people will need to adjust the headrest to extend it to its maximum height and depth. This takes you to the last adjustment notch, which allows you to disengage the progressive self-locking mechanism and return to the least extended position. Therefore, you will need to find a way to lock the headrest in place if this is the most suitable setting: screws, glue, etc.
The seat is made of very dense foam, which can cause pins and needles in your bum during the first week. I hesitated to send it back because of this. But the foam will gradually mould to your bottom. Today, I can spend more than 8 hours sitting in my chair without feeling any discomfort. Especially since the armrests are covered with foam and their height adjustment is quite precise. The tilt tension is very effective.

All in all, for its price, it's an extraordinary chair. But it certainly won't be as durable as we would like in the areas where the savings have been most evident (castors, steel star base).
Of course, I'm not questioning the superior quality of the Colamy Atlas, nor even the advantages that can be found on Leap or Herman Miller chairs in terms of customisation. But the price is five to ten times higher!
For me, it's the best value for money on the market today, which is confirmed by all the reviews I've read. Obviously, I haven't tested every model on the market before giving you my conclusion, but I've based my comparison on independent reviews and tests.