Now this is overkill

Why would you want to have 400 hours of available recording time on a replaytv. I have 2 40 hour units and have never run out of space. I just copy shows over to my media server if I have not watched them in three days. It happens automatically. Never have even come close to using up the space on the replays. Here is a link to a guy that is playing with a 400 gig drive in a replay. Soon he will be putting two of those drives in a replay to have a 800 hour replay407 hour 400GB Single Drive Upgrades – AVS Forum