Most of my heatsink comparison testing was done in the LZ7 and the L12S has been the top performer I've tested so far for sub 70mm coolers, beating the Scythe Shuriken coolers.So I am presuming by all the heatsink testing, you have done the ones that got the best noise/performances ratios are the L9a and the L12S
also thanks a lot for the reply as that is one of those things you won't know before you try it and would have been annoyed if my pc sounds like a hairdryer/desk fan when I boot it up for the first time
As you say the L9a would also be a quiet cooler due to the large distance between the fan and vents.
Cryorig have just teased a silent fan version of their C7, that may be a good choice as well.