The 6N1P is NOT a direct replacement for the 6DJ8/6922, although they are very similar. It has a different heater current requirement for one thing. I would definitely check with ARC first before trying this in your VT60. It would be worth the trouble in checking, as it is supposed to be a much better sounding tube.
Svetlana 6N1P in new ARC VS55
The new Audio Research VS55 amp uses the Svetlana 6N1P for it's driver and input tubes. My understanding of this tube is that it is similar to a 6DJ8/6922 type and may substitute for these types in "some" applications. This amp seems to be very close kin to the VT60, and I wonder if anyone knows if the 6N1P can be used in it or in any of the ARC pre amps that use the 6DJ8/6922, I.E. SP9,SP14, LS1,...? This tube might be a promising prospect if it will work as a sub, and they are dirt cheap to boot.