I personally recommend Samsung hard drives for silence. Seagates are supposed to be quiet too, but the one I purchased made this annoying click sound every 30 seconds which drove me up the wall (and no, it was not defective, Seagate described this as some special technology which keeps the head active and prevents damage to it). I replaced it with a Samsung which was even quieter and no clicking.
With optical drives I don't have much experience, but my NEC 2500A DVD burner is one of the quietest that i've owned.