I only have one, a Thunderbeast 30P-1. It is very quiet and accurate too. From what I have read here any of the higher end cans are going to more or less suppress the same.
I think you cant go wrong with Templars GB here on the hide right now. $600 for there Titanium 30 cal can and it can be taken apart for cleaning as well.
I have a AAC 762sd and have been pretty happy with it as far as sound suppression goes. But I have been a little irritated with how the can locks up on the mounts.
The Thunder Beast Cans and SAS cans get great reviews on here all the time and I would put both at the top of the list as being money very well spent.
I have a YHM 7.62 Phantom and it's a good bang for the buck but the Templar pricing for an all Ti can that has gotten good reviews is unbeatable for me. I doubt the YHM will see much use except on maybe a single gun just to justify having it once my Templars arrive.