Probably not in any meaningful way, since the KT77 seems to be rated at the same 25 Watts max plate dissipation as the EL34. That, and my impression is you'll need the power supply upgrades provided by the "Magnum" option to enable higher power outputs (and to supply the more hungry heater filaments) with bigger tube types (e.g. KT90, KT120).
There will almost certainly be sonic differences imparted by the KT77 -- not related to the power output -- just as if changing brands of EL34.
Happily, the non-upgraded Rogue Atlas/Cronus appear to exceed their stated power specs.
There will almost certainly be sonic differences imparted by the KT77 -- not related to the power output -- just as if changing brands of EL34.
Happily, the non-upgraded Rogue Atlas/Cronus appear to exceed their stated power specs.