Yours would definitely need the extra cables for the amp to work. I’ve seen the LEAR number on the amp so know it’s definitely correct and ATD did say if I had the amp ending 30 I’d need additional cables which one alone was £150! Definitely not the case with mine but still struggling to see why there’s no volume..First answer is: all cables takes unit to around £500 . They were doing a deal if bought together.
Second answer is: I decided to stay original and replaced the amp. So have no idea what back looks like.
Then we go on to I can't find part number xkq000020 , but doesn't mean it doesn't exist . Mine is xkq000030
Can you double check?