No head unit, just a tablet?

[J17K]

So what I want to do is just have a Nexus 7 as my source of sound in my car. I want to completely take out my head unit. I want to have an auxiliary connection as well as a source of Bluetooth. How would I achieve this?

I already have all of my speakers connected to an amp(in-car speakers to one amp and subs to another).

I was also looking at this: http://www.amazon.com/JL-Audio-CL-RLC/dp/B001UDQ1VI

Would that work for what I want to do? I want to be able to play my music very loud as well and something that I've read is that the Nexus 7 may need a new DAC to make it more powerful. I'm new to most of this stuff.

Also I want to add a wireless charge to the Nexus 7. How would I power this without using a head unit or cigarette lighter?

If any of you can point me in the right direction of what to do/buy that would be great.

Any feedback is greatly appreciated.

Also if anybody knows how I could use my steering wheel controls with it too that would be great but not really necessary. My car is a 99 Cadillac Deville.