Experience with Kenwood

Has anyone had any experience with the kenwood KVT-819DVD? I am looking for a new headunit for my car and I need a single din. I bought the new Alpine IDA-X305 for the compatibility with the iphone 3g but it's not what I thought it was going to be, so it is getting returned to crutchfield. I was looking at the alpine cda 9887 and 9886 but alot of what I have read just confuses me. I have had several systems in past cars but they have always been just coax's and subs with amps, basically best buy stuff. I'm really not even sure of the difference between passive and active. Please don't flame me I'm trying to learn.
Anyway I was looking at the Kenwood due to 4 volt pre outs, 2 usb connections and possibly navi. I have never had any kenwood products in my cars so I am kind of unsure of them. Any help/recomendations would be greatly appreciated.:bowdown: