On the Mesa/Boogie Blue Angel's headroom
There are probably a few things contributing to the perception that the BA has little headroom.
First, although this is one of the cleaner M/B designs still in production, it is a M/B amp and it has one more gain stage than similar 6V6 or EL-84 amps from other vendors. That third gain stage means that you're almost certainly going to run into preamp distortion as you crank the volume.
There's an internal trimpot that can be adjusted to change the amount of drive to the power stage. If you turn this up to get more drive to the power stage, it could help to increase both the apparent headroom and the amount of power-stage distortion at higher volumes. The down side of making this adjustment is that it'll probably also increase the idle hiss -- there's just no way around the fact that you have two cascading gain stages after the volume control. A lower-mu tube like a 12AY7 in the V2 position could help to give the amp a bit less gain and a little more punch. Keep in mind that both the V1 and V2 tubes must be quiet on this amp.
Second, the BA is a small-bottle cathode-biased amp. I know that some of you can cite conterexamples, but I generally find that large-bottle fixed-bias amps have a faster attack and less compression - this contributs to a sense of having more headroom.
Finally, the speaker is important. My BA came with an Eminence speaker which had an extended high-end. This made the amp sound very bright and punchy - more so than I liked. The normal speaker for the 1x12 combo is a Celestion 90, which is very good for that Boogie midrange lead sound.