to my ears, with high impedance cans, the phonitor is far better than the p1u. it reminds me a lot of a push-pull tube amp, with lots of control. however it does have a relatively high output impedance, so it may not be a good match for, say, Grados. with these lower impedance cans, I didnt like either of these amplifiers.
the b22 is a fantastic amp, but do not shy away from the dynamid. it is still a force to be reckoned with, despite the fact that it is an older design, with lots of power and a quick, agile feel.