I would reccomend the 80 GB Western Digital model...WD800JB..have seen it in action and it is quiet also not many around with 8mb buffers under 100gig(well most i see are the 120gig upward drives)Quote from a review i found "While we couldn't even hear the Barracuda drive with our ears next to it" also link here >Click
If you want silent, go for Seagate. Their new Barracuda V is supposed dead silent. I just ordered one (20 mins ago). Don't think they have 8MB chaches though. Second choice is WD since they do. I have a 120GB WD SE and it was very quiet. Now it's whining and I'm having it replaced.
I've been running Western Digital for years (ever since the days of Windows 3.1 and 486 computers), and have never had problems with them, unlike other manufacturers that had compatibility conflicts. Of course, the conflicts may have been fixed years ago, but I guess, in terms of hard drives, WD has my brand loyalty.