i didnt see the 800.1... saw an 8000.1 but i dont think thats what you were going for. looking at specs for the 400.4 is going to give you 55watts. there are several companies that make compact amps. usually for motorcycle purposes, but you can use them for a vehicle. my biggest concern with these small amps is the components used and the power limitations. it will definitely give you more power, but trying to get lots of power in a small space generally equals lots of heat. behind the rear seat will act as an insulator and trap heat. especially if you are putting a lot of equipment back there. i am not familiar with this brand so i cant speak for its build quality or longevity, but its in comparison to other companies mini amps. being that you have a 17 you have the sony system so some kind of sound processor is highly recommended as you dont have the ability to add the zen module like the b&o system