I have an old Orion that puts out about 60 watts @ 4 ohms per channel in 2
channel operation but jumps to 260 watts in bridge (mono) mode. I was
wondering if the output in bridge mode is as clean as say two channel
mode?
Is there a lot more distortion present in bridge mode?

There's less distortion involved with bridging when you take into account
the possibility of clipping.