DOA means Dead on Arrival.
Please wait for a response from the correct channels. MP4Nation AND FiiO before trying little science experiments or asking questions for alternative fixes. Because why go for alternative ones when the primary channel is easiest.
If you want to, you can. It's hard as hell to close back up though. I do not know if it will void warranty. But I would only recommend you attempt to open, diagnose, and close it up if you are dilligent and patient. Right now, you do not seem to have patience (no offense) so I would not recommend it. I personally am a pretty patient person already, and was on the border of raging getting the X3 back together.
Overall message: We(I) are not device support staff of FiiO's. For problems that don't involve general questions about the unit. Waiting for FiiO support to offer you a solution is the best solution. So please just sit down for the next two days and wait for a responce from market or support @ FiiO.
I haven't heard a reply from FiiO. I have however been in talks with MP4Nation and they want me to send the unit back. They also told me I can't open the unit as it would void warranty. I have a question about that. FiiO designed this device so that the battery is user replaceable. Aren't we allowed to open it up then to replace the batteries when necessary? If James can confirm this then that would be really helpful.