My Sony-Ericsson MW600 also shows "unknown" no matter what I choose in settings. It is connected on Sony Xperia T with the official latest 4.1.2 and Poweramp 209-534. But the inbuilt Sony Walkman app shows track info OK. More, if I use Poweramp after walkman the MW600 display still shows the last song played in walkman and it doez not change to "unknown". So I guess Poweramp just does not interact with MW600 display or simply does transmit wrong info. I can't remember for sure but it worked in 4.0.4 with 528.