Headunit + Components - what else do I need?

Nillaz

You're going to need a couple things...namely a wiring harness, antenna adapter, speaker wire, and possibly spacers for your speakers. You could in theory hack up the wiring in your dash and wire everything direct but I would STRONGLY advise against it.

Anyhoo, I don't have a direct link but I believe the parts you need are:

Metra Part # 70-7552 (wiring harness)
Metra Part # 40-NI22 (antenna adapter)

You can get them lot's of places, though they can be obtained relatively inexpensively at Amazon.com

You will also need to run new speaker wire for your components. If you're not using an amp do speaker wire runs from your HU to each of your crossovers (2 total) and then individual wire runs from your crossovers to your midbass drivers and to the tweeters (4 total). You don't need anything crazy, 16 gauge wire should do the trick and still be fairly easy to work with.

If your components don't come with usable spacers you can make some yourself or get them from someone like Zenclosures.

A dash kit is optional but if you don't use one I believe you're going to have a slight gap with a Kenwood HU. If you want the dash kit it's:

Metra Part # 99-7607B

Hope this gets you on the right track!