What you need is a thing called power attenuator.
Mark-series is not something we could describe with the word "silent". You can use your master volume to make it be very silent, but what you get is not what you really want to hear. In some low volume levels amp practically dies. With decent power attenuator you can simply make your normal sound and then roll it down using one knob.
People keep telling that those drain your sound. That's a nope. Some old, very badly designed ones did, but today that type of attenuators are rarely found. Even with 100 euros you can get a decent one (can't advertise brands here, i think). What you lose (if you have a decent power attenuator) is the part of sound which comes from pure power. That means simply volume. Sound is there, sustain is there (however your feedback does disappear). However for those who don't understand how sound works, effects of lower volume may seem to drain the sound.
What you don't get with it, is shaking floor or image of headroom starting from whisper and rising to friendly noise of 1000kg bomb exploding in your ear. But the headroom is still there, althou it's not as clear anymore. Remember that the amp still works exactly the same way than it did before the attenuator.
Also some speakers go darker when you roll your volume down. C90 doesn't do that too badly althou some minor high end sound loss is noticeable. And if you get some more expensive gear, there are attenuators that have tone controls to fix it.
Power attenuator. Everyone playing tube amp's at home should own one.