Another cool site is Plycon.com, they sell any kind of fan and adapters, I personaly bought a 92mm delta with an adapter to se on the Volcano 6 Heatsink. I didn't get it yet, it should get to me on monday, but I belive that it will be VERY loud, now I prefer it to be so than to have high temps. Your temps are normal for a thermaltake Volc. 5 But if you really want to lower your temps you will have to deal with loud fans, even the Sweefe 462 mounts a 80mm delta on it that makes it loud. The only solution on a silent fan is to buy a Silverado, I was going to buy one but after 5 days of reaserch I decided that it wasn't worth it. If you set it to be quiet it doesn't cool a lot and if you set it to the highest spees, 12V, it isn't as quiet as one would like. So the best solution Is to change to a high power fan. See this:
The Volcano 6Cu has a temp of 51C full load with a 32cfm fan
The Volcano 6Cu+ has a temo od 46C full load with a 38cfm fan
The heatsink is the same, the only change is the fan.
The Sweefy 462 has temps at full load of 40-41 C with a 68cfm delta fan
So
If you put a 60-100cfm fan on any heatsink it you will get the lower temps you are looking for.
That is my point of view.