Pretty limited if you need all the slots, otherwise that noctua would be the best bet. The prolimatech megahalems seems pretty good, although I think that would be about £65+ with fans.
Is the Frio not doing the job?
In terms of fans:
In terms of quietness Noctua are probably king, but obviously they are very expensive. I've used a fair number of different fans and this is my very subjective take on them all.
Sharkoon Silent Eagles shift a lot of air at 2000 RPM but are pretty loud, 1000 RPM they are reasonably quiet. They are not the ultimate fan ever, whatever Bit tech says.
Xilence, had a few of these, the 1300RPM ones are cheap, reasonably quiet, but by no means silent. I've got a red bladed PWM Xilence as one a CPU fan, but it doesn't shift enough air really.
Gelid fans seem to be very quiet, and shift reasonable amounts of air at low RPM, but on the other hand its still pretty middle of the road.
Yate Loons are great value, I've had a fair few, quiet at 1200RPM, they can get pretty loud by 2200, but they still aren't as loud as the Silent Eagles. That said they are pretty cheap, at £5 a pop.
Scythe Gentle Typhoon, these are currently on my big radiator, they shift a lot of air at 1450RPM, but they are still noticeable noise wise (maybe as loud as a 280GTX idling, you know they are there, but they aren't that distracting). I dare say the 1150s are quieter.
Suyon 38mm, this shifts a lot of air, but unfortunately isn't quiet, great for temperatures, but there are better fans out there
Deltas, not owned a delta, but the 38mm ones could go up to 4000RPM. I have heard one, for an accurate idea of how loud this is, get a hair dryer, switch it onto cool, then point it down your ear.
