Thanks, Jon! The old computer is hard-wired to the network and I'd have to run another cable to hardwire the new one - which would doubtless come with WiFi but that can slow downloads. Networking the two and sharing data does make sense and running a new wire isn't difficult. I'd have to look into the possibility of setting up the partition to dual boot in a computer I buy with the pre-installed OS. It used to be that both OS had to be stored on a certain part of the disk in order to be reachable when the computer boots (and offers the boot choice) - that may be moot with the SSD.

I was looking at switches for computers sharing monitors possibly like this, but it would take a lot of reading of reviews and comparing vendors to settle on something for this task.

That is an idea about putting the computer in the front room next to the big television. I could hard-wire it there, again, running another wire would be needed because the BlueRay player is hard-wired by preference, to keep download fast and the highest quality from places like NetFlix, but it isn't difficult. (Or it could replace the BlueRay player, but it's a bit more clunky.) I would use an HDMI cable to the television to view things recorded, and still have it available to network for design work. But then I couldn't share monitors without really really long cables. . . so, perhaps not.

This is early days yet in the planning process.