Collectors are interested in most Revox units,Revox made some very hi end gear which would lead me to believe that the rest of the gear in the attic is also hi end.Look for names like Quad,Mcintosh,Dynaco,Telefunkin,Marantz just to name a few.
If you find any manuals or factory packing material do not throw any away,any related materials will add value to a collector.
Im not a collector of RTR tape machines but i do collect vintage amps & preamps,if you post the other models that you found i could help with the valuation.
Depending on what you found you could be looking at some serious money