Ive visited Space and Aitsulab showroom yesterday. Space ergonomic pro is basically same with Sihoo M57 except for several additional flexibility (can move the seat forward and backrest upward). Material also almost same. Both are good and comfortable enough for its price but if you dont need the extra functions can just buy M57 because it has the foot rest option and cheaper.

I ended up buying Sihoo Doroo c300 btw. Pricier but more comfortable and i like the narrower seat more as Im only 5'3 56kg. But C300 is not suitable for taller and fatter person. I think you should try first before blind buy but space ergo/M57 is safer choice if you still wanna blind buy because the design is quite universal and can suit wider range of body type.

Premium chair usually will stand for years

Last time i bought RM500 entry ergo chair during MCO can even last me few years.