Welcome, Craig. And I think the skewedness comes from being a trumpet player, of course you're going to say it doesn't get loud enough. Just kidding, dsavitsk has a thing for low gain and the K501 is pretty inefficient. So much Shosty, but no love for the 5th?
I have a lot of experience with the K501 with K501 and with K601 pads, as that is probably the headphone I have listened to the most, but I sold it awhile back. What I found weird about the sound is the soundstage is big but oddly shaped and the midrange can seem shouty at times because it is brought to the forefront while the bass and treble seem distant. That said, I wouldn't mind owning another pair at some point.