Going to the garage this morning to see if they have another Canton system to compare. Had the boot floor up and there’s very little coming out of the sub even with it set at max.
According to the chaps on the Facebook forum anywhere above +3 the boot and rearview mirror starts to vibrate!, mine certainly doesn’t, even on +9.
Please excuse spelling/typos. Apart from being a clot it turns out I had one on my cerebellum that's now causing various problems!