Advice on how to get FedEx to pay up on damage

HELP! I recently shipped a subwoofer via FeEx ground. I put it in a heavy box with a lot of packing around it including about 6 inches of padding on the top because the speaker and grill are on the top. I marked the box all around with bright red arrows labeled "this side up" since it was very heavy and turning it over could damage it. Guess what. The grill and speaker were damaged and FeEx is claiming it was not properly packed. I figure they turned it over. Does anyone have any advice on how to proceed with this? I have spent hundreds of dollars shipping via FedEx recently and this is the first problem I have had. This is complicated by the fact that the speaker is now 2000 miles from where I am. Any thoughts?