The first thing you need to do is to forget about getting overdrive from the power amp for bedroom practicing. That approach is only one of a ton of ways to get good OD sounds, and on certain models of amps there are many much better ways to go about it. This kind of shatters the idea that all tube amps need to be set to their power amp distortion point to "sound good". It's just not true, and hasn't been since the late '60s when cascading gain stages were thought up. They only need to be cranked to get their own overdrive and in cases like certain Mesa amps, the preamp is king and the power amp only makes it louder, so it wouldn't work very well anyway. To further that idea, tone itself is not dependent on power amp distortion, or any amount of distortion for that matter. I can get a great tone with no distortion you can easily hear, and someone else can get a power amp raging and still get a bad tone. Get it?
That brings us to the point that you are playing heavy metal in your room, so good preamp drive or a good metal style pedal into a clean power amp is going to be your best bet anyway.