I don't know what is the C106, but I know many people had faced simillar transistors rattle in their Gp2Xs, and all of them ended talking to ED and solved their problem (either by telling them what to do, or by fixing it for them), if you can't wait for ED to reply to this (it is new year's eve in Germany too
) you can check the following things to make sure nothing major was destroied:
1) Overclockability
2) Power through PSU and batteries
3) Speakers, check for noise or if both stereo/mono are working well
4) Videos, if they are stable
5) Vektar demo, it has parts of the code especially wrote for GP2X's hardware
6) Picodrive, use the other core for sound emulation
7) Any other tests you might think off