That's a great point about potential damages if trying to rebuild the Compaq in another case. I suppose I shouldn't make the move to a new case until I'm willing to replace the motherboard if necessary. At least that way it wouldn't be a big risk.
Technically, I don't really need that many hard drives. But I do have a lot of data, and a bunch of external hard drives that would be nice to put internal. I also tend to always have extra drives that I prefer to make use of rather than to spend money on a larger replacement drive. A lot of current systems also support RAID options, which I would like to try out. Plus I also like to have an internal drive to do frequent backups. (An external drive is still needed for backups on a less regular basis, but for the frequent stuff a separate internal drive should be sufficient.)
But the new system with the stock case, maybe with a new power supply, should be plenty sufficient to handle an OS drive, a data drive and an internal backup drive. My external drives can stick around until I either upgrade next time or I create a network storage server.
Come to think of it, with my newfound knowledge about the internal components, I might just take a look at beefing up my old DELL or Compaq (one will be my wife's and the other will be a Linux box) to handle some extra storage and share the drives. (Will have to look at whether you can share a Linux drive to a Windows computer.)
This stuff has really opened up a whole new world to me! I just hope I'm not going to get in over my head!