Don't have any personal experience of this model, however, I did upgrade to a lesser spec Pioneer unit with Navi in my van. I thought i would need an amp etc but the sound quality of the Pioneer on its own was adequate for me. I guess it's all a matter of personal taste, I was thinking about upgrading the Bose in the Zed to another Pioneer unit and the advice I was given was that any additional kit was not entirely necessary as the Pioneer would improve the sound quality over the Bose considerably. My suggestion, therefore would be give it a try and then decide if you want to spend any more. As far as I know you can integrate with the steering wheel controls, have a look at Car Audi Direct, they tell you exactly what you require but shop around as they are not the cheapest.
Hope this helps a bit, no doubt there are people on here with far more knowledge than me, they'll be along soon I expect.