Got to thinking more about how to make the best use of resources with the computers. The biggest issue is ergonomics. You can only really practically use two keyboards at a time. So if using more than two computers you prefer to have more than two keyboards/mice, but it's hard to access them without moving your chair, unless you can use VNC. At the moment I have a love/hate relationship with VNC because I haven't been able to make it run as a service on any of my Linux computers and therefore work out of the box every time. Also X11vnc is less than reliable and crashes quite frequently.
In terms of the two computers that are most frequently used, the serverpc that only has 16 GB of RAM should be boosted to 32 GB at some point, probably with a new mainboard, and its existing mainboard gets moved into mediapc, which in turn its board gets moved into the 4th computer. The main issue with running lots of applications on a 32 GB computer is when one of them causes it to crash. I'm still looking at the optimum way to use the 3rd or 4th computer to run some stuff such as email and spread the load of map resources onto the 2nd computer so it isn't all the 1st computer, but it's a tricky process to try to work out the best way of making that happen. I think it will be necessary to focus mainly on the two computers with the keyboards that are easiest to reach that will run virtually everything, so mediapc will stay media and ministrypc will stay ministry.
Running the day to day stuff in a VM on mainpc is a possibility. We are looking at what is internet based and doesn't have issues with local resource access. It's possible I may put email onto mediapc and possibly some other resources because it isn't used for that much and occasional access via its own keyboard, which can also be switched onto one of the main keyboards, is viable. This is different from using it for image display, which is what I have already experimented with, which often runs into problems getting updates from mainpc over the network. Internet based stuff like email doesn't have that limitation.
So probably the next goal is to get serverpc up to 32 GB, there is quite a bit of cost to this so it would end up happening in stages. Of course, I presently have no budget for this, so really it is a dream for the present. We just keep working with our current resources for now. If I can make VNC work properly on mediapc then it will be easier to do stuff on that which I find hard to use it for at the moment. However doing the new board for serverpc and putting its board into mediapc would also help because mediapc would have enough resources to run more stuff and over VNC it would be very good because I am using VNC to control the screen, which is still being displayed, unlike RDP where the screen turns off.
I will have another look at VNC support for Debian and do some testing with tightvnc as it seems I should be able to make this work and then mediapc in particular can be used for more things.