Hmmmmm, anyone making active cables for these?
Well you kinda of loose the idea of the m260's and m60's if you where to use a active cable > PFA solution
The m60's from what I understand are a stab at the old km84 as they have output xformers
The m260's are tube based
The Telefunken design does not allow for a realistic addition of an active cable as the capusle is only a capsule and only has 2 conductors present (polarization and gnd)
You may be able to add a jfet based impedence converter with extension cable but you would need additional power for that (prob 4-10v depending on the design/FET)
They have looked into an active solution but I have no idea where this would stand in there priority list or how far it has gotten.