I brought this headunit the other week. Fitted it, and had the same
problem as you, not remembering sound settings. It came with its own wire loom which plugged in straight away, but i took a gamble and brought the one in Halfords aswell, and this solved the
problem. It now remembers all settings.
And the SD card wont read 4gb sd cards
ive done some research on the net and apparently the largest it takes is 2gb so ive ordered one of those to test it. But i can still use the 4gb in in the front USB which is cool