Next step on my self-hosting journey - Feddit.dk

Hello everyone. Well, I’m here to ask for your insights and knowledge. I have been self-hosting for almost a year already. Mainly proving things like Jellyfin, jellyseer and all the ARRs. All of this with a modest Raspberry Pi 4b using DietPi OS (which I think is great!) Now, I want to move to the next stage, acquiring a more powerful machine. What do you recommend for: A) Mini PC. I want it to fast and with a huge storage (being able to increase it easily) B) SSD or HDD. Which ones. C) Operative System. I would like to stay on Linux. Any other recommendations? Finally, I have an adjusted budget, but pretend to save a bit more to have something nice :) Thanks!