Since you seem to be collecting a large amount of information, it might be a good idea to get a RAID card and start using a redundant backup system as your "just for data" drive. Having that system myself saved me from losing a bunch of important data when a brand new maxtor drive failed after two months. A RAID card will also let you add plain old single hard drives to it, and use them like a normal drive (at least I think they will) so getting a raid card with extra slots gives you the capability of redundancy if you want it later, and also gives you extra IDE channels for your other drives. They also remove the problems windows has with large hard drives, since they handle drive access themselves, and I think they reduce the CPU usage during hard drive access too.
That's in addition to their ability to make your hard drive transfer rate much faster, but doing that probably requires more hardware than you want to buy right now, unless your other two drives are the same size and same amount of cache.