I would say that a 180mm front rotor would be more than adequate for your needs on the Anthem. And certainly cheaper than replacing the whole brakeset. How 'used' are the brakes? Perhaps a good bleeding and clean at the same time would help.
What he said…
I'm pretty sure your Fox forks are not covered under warranty with anything bigger than a 180mm front rotor fitted anyway, so this is worth bearing in mind.
Your Hayes brakes aren't the last word in sophistication, but as much as I love Shimano brakes, I don't think you'd find the stopping power you require just by switching brands. And certainly I wouldn't be putting a set of Saints (as stated a "DH" brake) on an Anthem. At just shy of 15 stone you're heavier than the average rider sure, but not my a lot.
Give a 180mm front rotor a try (about £15 for a rotor, about £6 for the requisite adapter), at least it's a cheap option. And whilst you're at it, see if the brakes need bleeding (are they spongy or not?), and possibly/probably fit new pads all round… My favourite pads for pure stopping power terms are the A2Z blue compound. I've used these pads for some time, they're more powerful than anything else I've tried (EBC redstuff aside but they last minutes!) and yet seem to last a long time too!
Thanks, some worthy points in there.. I think your right abouut the hayes brakes i have, they are bottom of the line.
I was thinking it would be nice to have the all shimano groupset look by ditching the Hayes.
Any recommendations on rotors? or are they all pretty much the same?