Hey Neil, you don’t have to get your install/setup perfect the first time. I’d recommend you install Roon on the hardware you currently have available, and if at any time you need to transfer your Roon installation to a new machine, give us a holler and we’ll help you out.
As far as hardware requirements, check out the FAQ post here, and @brian’s highly informative post on hardware requirements here (also linked from the FAQ post). I think this should help you out!