Thanks all for your replies. My older RealTrax is tending to break at the connections, I guess it's getting too old and, yes, the connection of track pieces can be a bit awkward. The idea of connecting the two could be a bit jarring visually, so I think I'll just keep two independent loops and eventually wire them both to the TIU with my pair of Z-1000s powering them until I spring for a Z-4000.
The only command locos I currently have are all old ProtoSound 2, I'll have to get them running again and maybe think about upgrading them to PS3. I do have what I think is a very nice scale Williams GP38 AA set in Chessie livery that I'm going to take to the local PS Upgrade shop and see if they can convert it for me, but pretty much everything else I have is 'O27 scale', so we'll see what the cost will be first.
