YOU asking the N00bs for advice
Well I would say if you want quiet drives Samsung are very good.
I have 2x160gb and 2x250gb raid 0 arrays on mine and they are Western digital 16mb cache drives (from memory)
I would say try and get 16mb cache minimum drives if you can.
A review bit old tho.
http://www.techspot.com/reviews/hardware/seagate500gb_wd400gb_hd/anyway who am i kidding im sure all the main players in the HDD market are decent enough the differences will be in milli seconds.
Just use 4x raptor drives instead!