If it's anything like CanJam, they'll let you get pretty hands-on with stuff. Bring any smaller stuff you feel comfortable bringing in a backpack. Remember that they are probably going to have more standardized options, so make sure you have at least a 3.5mm cable for earphones and 1/4" cable for headphones. Bring your own eartips for trying different earphones. Again, I don't know how different the Paris show would be compared to CanJam SoCal.