Hi, I was quoted about £120 for two speakers to go in the rear. This is a local reputable company that I went to, they did a little research and said the only issue they could see if that they may need to make custom speaker mounts as they couldn't buy them for the Adam as yet. They were honest and said they hadn't worked on an Adam yet but the quote stood at £120 for two decent speakers. That said, I will be going via Vauxhall who will do it for slightly more but then I feel assured any issues will be put right if it gets messed up!