I recently replaced my H80i GT with a H115i. The noise is really more about the fans regardless of which manufacturer you choose. Corsair rate their SP140L fans at 40dB, which I didn't even test but any fan running at 2000rpm will make a racket. I used Noctua iPPC 2000rpm fans on mine (31.5dB) and they're fine. Barely a whisper running at around 700rpm and keeping the CPU at around 20 degrees idle and 50 degrees during Intel Burn test and Prime95. Of course, on an OC profile they're going to spin up to keep the temps down.
Do some research on fans and you'll find a number of fans quieter than the stock fans from most of the AIO vendors, your only problem will be budget - especially if you go with the Noctua fans.
Incidentally, the pump is slightly louder than the H80i on the H115i, but it's barely noticeable.
Hope that helps!