Currently have a modded* reserator 1+ serving my 2600K while I'm mid-build re-fitting my new radiators.
Down-clocked to 4.3ghz to play it safe, max stress temps are ~55c, though I didn't bother playing with the voltage so its still at 1.39v from my 5ghz clock.
*Modded = removed fitted pump, sealed un-needed holes with silicone using an internal D5 pump, 7/16 ID tubing and Raystorm CPU block.
I wouldn't be too comfortable adding a GPU into the loop using just the reserator to get rid of the heat.