Dude. That amp seems badass. That is a good price for a handmade amp. I don't think the gain past 5 getting muddy is a big deal at all. As long as you get the tone at that point. It's a good thing you can hear it and back off. All the amps I have built are that way.
The youtube vids on this one didn't do it justice. There was a few by a guy named Dave playing some 80's metal Lynch type stuff and you can hear that the amp has some balls on the sustained notes.
It probably will not keep up with a hard hitting drummer. But if you can mic it into the P.A. or slave it into a power amp, you can get loud enough.
