You usually match a power cord to particulat component so they don't have to or should not be the same or even the same brand. That said, if you want top of the line they might turn out to be the same, maybe.
It varies which component will be more sensitive to the upgrade, it is hard to advise. In your case I would probably first upgrade your tube preamp cord, then the source and the amp the last.
It varies which component will be more sensitive to the upgrade, it is hard to advise. In your case I would probably first upgrade your tube preamp cord, then the source and the amp the last.