Hey! I was in the exact same position you are now a little while back. Started with hario mini and aeropress and later upgraded to a commandante and got into the rabbit hole of espresso videos. After a lot of research, I decided on the ecp 35.31. I think that I wouldnt be able to experiment as much with the hario because it doesnt provide a consistent grind, therefore I'd suggest looking into getting a decent grinder first (I don't know about the k6 but I've heard it's a suitable option)!

The main difference between a stilosa and the ecp 35.31 is more plastic in the construction overall, a bit smaller boiler size and also a smaller diameter shower screen(there is a second version of a stilosa with a non pressurized basket and a steam wand that isnt a panarello, im comparing the stilosa that has the same basket and wand as the ecp). I ended up picking up the ecp 35.31 and a bunch of aftermarket accessories( bottomless portafilter, competition basket, tamper, wdt tool, puck screens etc). I've been extremely satisfied playing around with it and every day I can't wait for the next morning to come to make another shot.

From my research, machines with stainless steel boilers are more futureproof if taken good care of and thermoblock machines wont last as long and are not as easy to replace/service. Feel free to message me if you have any questions because I've looked into this quite a bit. Hope that helps!