Also consider some dampening material such as :-

Akasa Paxmate Acoustic Absorption Mat
http://www.overclockers.co.uk/acatal...sories_36.html

or AcoustiPack Deluxe
http://www.kustompcs.co.uk/product.php?view=2048

or Cooler Master Sound Reduction Kit
http://www.kustompcs.co.uk/product.php?view=2058

or Magic Fleece noise killer
https://www.chillblast.com/productsdetail.asp?PGID=25

And cut out the mesh part of the case behind the 120mm and replace it with a wire fan guard.
http://www.overclockers.co.uk/acatal...sories_34.html

And you could give a couple of these a go on the Papsts as well
http://www.overclock.co.uk/customer/...41&cat=&page=3

And one of these for the PSU
http://www.overclock.co.uk/customer/...42&cat=&page=3

and i think that's it, should be about as quiet as you can get without going to extreme measures