The reason for why it struggles with mp3's higher than 192kbps is that you problebly have a 40MHz DSP. When I had my A4000 with Delfina Lite, I overclocked it from 40MHz to 66MHz. This helped a lot! After the upgrade, even 320kbps mp3 songs worked fine! So, if you find someone that can change crystals for you, do it.
I am a Delfina fan

Love the sound of it! Best there is...