The 2-piece caliper 525s are poor. I've had a set.
There is an o-ring in between the two caliper halves and once that starts failing then it's pretty much game over as they will always leak even with a new o-ring (they're fitted in the factory properly). Mine failed after about 1 year. Not impressed. The power was also very disappointing and the pads died really quickly. I would never buy them again. A second hand set of XT / 2-pot Saints would cost about £100(ish)and are much much better. More power, more modulation and they're so much more dependable.
Shimano SLX are another good call if you're buying new. The lever is really nice and they are very popular as a budget Downhill brake, but they come at almost trail-brake prices. Bargain!
I'd bag a set of Juicy 5s. They're an extra £10 an end but more than worth it. The power is actually pretty good, they aren't that heavy and have reasonable modulation. Either that or a second hand set of Hopes, something like a Mono M4 (probably about £100-120 for a decent set, but Hopes can be made to feel fresh out the box easily because spares are easy to get hold of and they're designed to be rebuildable)
As for your current brakes I wouldn't touch Hayes with a bargepole myself as the pistons have a habit of rotting unless you give them loads of TLC (not likely to happen if a baby's on the way), and that appears to have happened to yours.