Well, you did mention a "water cooling accident." Had water gotten into the PSU? Are you certain everything else was dried off? Your rig should not have stressed an 850W PSU.
Jonny gave this one a 7.5. When you replace it, a 650W model from Antec, Corsair, Seasonic, or PC Power & Cooling would be good choices. That's for your current rig; if you planned to add another HD4890 later, get 750W.