Hello!
I thought I should update this thread on what I've finally settled after trying a few different routes.
First I tried to go the official way, which ended up being super expensive if you live in Spain. There's some more accesible options on Germany through Voleatech but still quite a bit with the power you get. Don't get me wrong, this would be the perfect option if this was a mission critical equipment, but this is just for my home network.
Then I tried going the virtualisation route but I found some problems and/or limitations with KVM when trying to route gigabit speeds. I'm currently on 500/500 but pretty sure in a few years from now we will have 1000/1000 as my ISP has been almost duplicating speed between 2-3 years. Not so future-proof. Also was a bit of a pain in the ass if I had to do stuff on the server that my internet will be also off.
And finally arrived to what I think it will be the perfect solution, yes you guessed it: bare-metal installation. I had lying around a cheap PC I built last year for my crypto miner project: Asus prime z270-p + Intel G4400 + 4gb RAM (that was around 160€ new). I'm going to add a SF450 PSU, SSD next week but already got the Intel i350-t4. Power consumption currently is around 28w on idle and 35 when routing gigabit with ntop, suricata, pfBlockerNG and a few more). Should be a bit less when I receive the SSD, currently is on HDD.
Hope this could be helpful for someone else looking at build its own pfSense box. I will update with final numbers once I've all in place. Maybe even some pics!
Thanks :)