Need a completely silent external hdd enclosure

[boognish100]

Can anyone recommend an absolutely silent premium external hdd enclosure? I'm having a nightmare finding one. Google has been saturated with 1000's of cheap and nasty hdd enclosures that all promise a 'quite operation', but I'm not really convinced by them.
I've already got through two external hard drives in the last year (a freecom 400GB FHD-3 and a Formac 500GB Platinum XTR), both off which went from being reasonably quite to almost unbearably noisy within just a few months, the fans made a real racket on both models, this short life span could be down to the fact I have to have them on 24/7. So I've decided to try the internal hdd + enclosure combo.
I don't mind paying a premium for the enclosure. I plan to use a 750gb seagate baracuda, I'm not sure but I'm assuming the higher the capacity, the more cooling is required. Ideally I want a none-fan based cooling system, something that isn't going to deteriorate over time. The hdd will be on 24/7 so I need something durable that will keep the hdd permanently cool.
Any suggestions appeciated!