Current set-up is Hope M4 (old style) front and rear with 8 inch rotor on the front and 6 inch on the rear.
Although they're okay (still squeal a bit at low speeds) they've never been really powerful.

So my question is…stick with what I've got and maybe get them serviced or try different?

Mainly do xc riding btw.

perhaps they just need bleeding? otherwise I'd go for Formulas, mine (k24's) could stop a train!

they've never been really powerful.

Do they stop you? Or are you constantly thinking, "I might not make this corner…"

Depends what you want from your brakes really, as bizarre as it sounds I don't reckon one finger retina detaching "think and you'll come to a stop" brakes are all that when it comes to regular XC, On the World Cup DH curcuit when the dab of a brake means a couple of thou on the finish line, they have their place, but for just messing about in the woods, then they just **** up your flow. Fresh bleed, new pads properly bedded in, is probably all they need.