Interesting, and fairly informative by DRTV standards. I have a few Pentax lenses, but they're all M42. To someone with a collection of K-mount lenses, this thing is probably worth investigating.
Birthdays are broken on H-C right now, but I found while looking for an amp comparison.
H/B/D, K/G! I always imagined you as the Great Cthulhu of headphone amps, lying alseep in the Class A City, dreaming of tube amp designs that would drive mere mortal DIYers insane.