Several of us in the Rogue group over on FBook have discovered that we actually prefer KT88 over KT120 in the bigger Rogue amps. My direct experience is with Apollos, but M180 should be similar. The KT88 midrange is better, and that’s where the Rogue amps need help - they can be a bit dry here. Triode mode doesn’t really touch it, but a good KT88 does.
KT120 will indeed improve bass slam, but that’s where the Rogue amps are inherently strong - they don’t need help here! Now on some of VAC’s amps we can have a bit of the opposite problem, and I prefer KT120 over KT88 there.
Gold Lion KT88 are excellent. EH KT88 are also good, just a different flavor - perhaps better tuned to "rock", while the GL are more refined.
The EH KT90 these amps used to ship with are a bit bright and not very "tubey" sounding. They are worse than either KT120 or KT88, unless your system is dark and needs a lift.