As an add-on... If you get the new systems you MAY want to consider Windows 10 Pro over the Home version. With the Pro version you can take more control of Windows Updates by using a quick tweak to set Updates to notify instead of fully automatic. I only mention this as I know that you prefer to have as much control of your system as possible.
LOL! I KNOW that it won't happen but I still advise, if doing a desktop system, that you build your own especially if you do not intend to keep using the old systems. They are really pretty easy to build and you have full control of the components. One BIG advantage is cost! My main system if bought retail is probably $1000.00 or more. I currently have ~$600.00 in the thing. The only real downside is that you have to deal with support for each component instead of have support for the entire system at one source.
If you do not intend to keep using the old systems my cost point is that you already have such items as the case, power supply, DVD, etc.. Basically you take the old apart and replace the old components with the new. I truly believe that even a novice can do this in 3 hours or less as long as they can follow instructions. I've not recently timed myself but I can probably do this in less than 90 minutes. What takes the time is all the updates and installs but even with a bought system you still have to do this.
If you ever decide to take on such a project I'm sure that you know that myself and others here would be more than happy to guide you through the process.