Just answering my own question now that i have the car. The USB stick does not play WAV files, will play MP3, AAC and WMA. Although does not play the WMA lossless type.
I think AAC sounds the best so will use them instead of WAV, at least i can get my entire music collection on just 8 GB, Besides the sound system isn't of good enough quality to tell the difference between coded music and lossless music. Unlike my 2600 w RMS PA system where the difference is very noticable.