intake fan : which papst or how to get the best of it ?

[Pilot]

I have a mid tower case I can mod at will.

I recently tried a noiseblocker 80mm s2 but even on rubber mounts and at minimum speed, the noise is not bearable.

I'd like to make another attempt and I seek for advices for the fan size and location.

I am going to fold a sheet of aluminium as if to wrap around my HD ( in a reversed G when seen from aside) and fix it to the bottom of the case. I hope that the sucking or blowing of the intake fan through this kind-of pipe would bring sufficient cooling. Otherwise I'll place some old northbridge rads i have available.

=> there are two questions :
- should I fix the fan on the case (soft mount) for it to blow on my hd, or after a cage surrounding the hd ( the birdcage seen in the forums) and sucking from the pipe/cage.

- which size should I choose ? some are fond of 120mm but others say they are louder even when at minimum. I'm aware it depends on the answer to the first question as the fan placed at the rear on a cage is enclosed by the case, and so the escaping sounds are not the same.

Thx for reading, and many more thanks for answering ;o)