Normally I'd recommend to get something like a Zalman VF700, but in your case, assuming it'll stay in the XPC there is no room for it. I don't know if there is a single slot cooler with a large fan that fits your card.

You need a different cooler, stock was too loud.
I don't know if the FX5600 can adjust the fan speed curve in the Riva Tuner or another utility.

Never thought about Riva Tuner that's a good call... I will try it.

How much better is a 5600 Ultra over a normal 5600? As i have both and both are 128mb variants and would expect the 5600 is quieter.

Failing that i may have to use a FX 5500 which is passive cooled but that starts to negate the whole purpose of building this rig which was to out perform my previous machine with a GF FX 5200 by a considerable amount.

I bought a Noctua fan for the CPU thinking it was that which was being loud but nope it's the GPU I had no idea they were so loud on the Ultra variant. I could always use the spare fan header and ghetto rig a quiet fan to it but i don't really want to mess with what is a pretty rare and cool GPU.