Thanks everyone

I'm leaning towards getting a 256 GB SSD for the OS and then 2 (or 3) 1TB drives for all the large stuff (databases, graphics resources for my 3D stuff, games, documents, videos, etc). The current desktop has 2 1TB drives in it and one very old 320GB (which still works fine surprisingly), and I've got a 1TB in the drawer that I bought intending to replace the 320 and never did.

The motherboard that Glenn recommended I get has *10* SATA 3 ports on it, so running out of ports won't be an issue, and the case has space for 8 3.5" drives.

Now, affording it all is another matter, as is finding the time to do all the rebuilding.