I have 09 x35d with 6FL and Premium Sound. I have DVD Nav. There is no USB port in the glove box. I thought that was only for 2010 since you have HD Nav system.

I use an external, USB powered HD for my music and it works great. I have a 120GB Western Digital Passport drive. It is formatted in FAT32 and I have a mix of mp3 files at 320kbps and WMA Lossless files. The X5 handles this beautifully.

I create the WMA Lossless using Foobar2000 and my library of flac files.

I can hear a difference between the compressed and lossless files. You will too.