Luca, regarding this part of your post “I would like to buy a louder soprano recorder to play irish-medioeval musik with some friends:…”
I think that if you are looking to get more volume the Mollenhauer Dream in plumwood would be a good choice but also a Ganassi model made by Stefan Blezinger (of course it will be much more expensive). You could also try a Yamaha soprano in grenadilla wood (baroque model) which to me sounds bright and edgy. All I know about Kynseker is that it’s a true Renaissance model with slightly different fingerings. Mollenhauer Dream is more of a hybrid.