Is it a good idea to remove the cat in order to have a bit more bhp and sound?
Any experiences, advice, etc...?

Same comment as regarding your query on tyres.

Though if it's an every day road car, it's probably more trouble than it's worth. As issues like, increased polution and getting it through an MOT come into play. Buy a decent back box (like the wonderful Scooby Sport) and get it chipped and run only on super unleaded, if you want more power.

Have fun.