Anyone here own a Rel Sorm III sub?

Hi all! My REL STRATA 3 makes a popping sound when turned on and off. Specialists in my city offer only delay relays. But I don't think REL makes their subwoofers with this feature. Thanks to your site, I was able to get rid of rustling sounds during playback by replacing the resistor. And I don’t know how to solve this problem. I will be grateful!
 
Resurrecting this thread as I'm another owner with a not very happy Strata III. All the proposed component upgrades are ready to roll, but surface mount C4 has been totally destroyed and I've got no way of knowing the value. Can anyone help?
Hopefully you already have this sorted, but it's likely the same value as C11.
You can just see C4 in stephen00 image above.