@marcfrick2112
Do you have any recommendations as to HD brands?
I have 4 Seagate Barracuda 7200s (120, 200, 2 x 400 GB) and they are all totally silent. No problems so far, and all but 120GB have 5 year warranty. Ok, the warranty doesn't cover the dataloss if the drive should ever fail, but the fact the manufacturer is giving all their drives the 5 year warranty is quite assuring.
Whatever manufacturer / model drive you get, always at least try to backup your most important data regularily. Catastrophic HW failure is just one way to lose data, the filesystem can get corrupted or files can be deleted by accident.
Regarding buying 3rd party HDDs (ebay or not): I personally wouldn't do that. There is no way of knowing what condition the drive is at, it could fail the next week and seller is long gone by then.