My plan of action will firstly be to check whether it's the head unit or amp at fault then get the circuits etc tested, so I'm going to try and find a fellow lexus owner with the same set up and swap the amp over hoping a bribe on the owners club forum will help! If you think £2000 for the amp is bad, try £5000 for the headunit!! Either way I would rather drive around with no sound than pay that kind of cash. It does indeed rain a lot here(!) but will only sometimes work so I can't rely on that and BOOMIN, have you seen the fuel prices in rip off britain!!