NAD - Artisan 15 and a couple questions?

[yardbird mac]

Today, I bought a BLACKSTAR Artisan 15 combo at an insane low price. I brought it home and cranked it up a little... WOW!!!

Now, I have two questions: Since this thing is so loud (the volume has to be pushed a little to get any real smooth distortion), who makes a good attenuator, and are they safe?
Second, this amp has two channels, but no channel switching capabilities, Will an A/B/Y box achieve that goal without harming the amp?