Klaus is the expert and he has helped me out with my install -but I think I can answer your question. Yes that system will work in your 03 with lux amp without any problems. It sounds like you want to do what I just finished doing. except I had to buy the luxury amp which you already have. I added an external cd changer in the back driverside wheelwell compartment, two headrest monitors and dvd player in the slot below the rear radio. I needed to pick up an auxillary audio interface to run the dvd audio through the system- the cd changer that I bought was vehicle specific and came with it's own interface. both interfaces were plug and play ant the install was painless with Klause's pdf instructions. The hardest part was running the wires through the seats for the headrest monitors. but anyway, that system will work for you but just wanted to give my 2 cents and say that you can do much better than there price if you piece the components together yourself like I did. good luck with the install. you can see pictures of my system here..
http://www.cardomain.com/memberpage/576320/1