I have a Power 2 and prefer the KT-88 tubes.
My preference is based on the power needed to push my speakers. I use the Power 2 to push electrostatic panels in a hybrid speaker. Haven't tried 6922s, but 6550s sounded much "thinner" in my application.
The people at partsconexion, which include the original designer for Sonic Frontiers have packaged upgrades for the SF amps and they all utilize KT-88s.
My preference is based on the power needed to push my speakers. I use the Power 2 to push electrostatic panels in a hybrid speaker. Haven't tried 6922s, but 6550s sounded much "thinner" in my application.
The people at partsconexion, which include the original designer for Sonic Frontiers have packaged upgrades for the SF amps and they all utilize KT-88s.