An inventory search is a search. They either searched your car and took an inventory, or they did not search your car and there's no inventory. "Yes impound yard still has that", is an incomplete thought - what were you trying to say? Have you actually reviewed an inventory completed by the police when they searched the car after impound? Even if not, do you know that an inventory was taken, with the inventory list in the hands of one, the other, or both impound lots? Then, quite obviously, the car was searched.

As for the intensity of the search, you've had your car repeatedly searched, while most people manage to go a lifetime without ever having their cars searched. It may be that the police took the opportunity to take a good and thorough look through everything in the car while they had the legal opportunity to do so. You seem to be guessing or stating your impression of what you think the police would or would not do. I'm not interested in guesses.

If your audio equipment was valuable enough to steal, it was valuable enough to insure, right? So did you insure it? Did you make an insurance claim?