07 Audi a4 S-line
 

So, I just recently bought an 07 Audi a4 s-line and I love it. I only have one issue with it and that would be that I have no way to hook my iPhone up to it to play music from it. Now I took it to Fry's and they gave me a few options that I could possibly do. Most of these options were replace the navigation with another that has ALL the bells and whistles. Then they told me $800 plus installation cost and I nearly died. So I was wondering if there was a cheaper and easier way to do it. I don't necessarily NEED the navigation system in it. They told me I could get a normal radio in there but I would have to buy the dash kit, then buy the antenna however with the antenna there are 2 possible ones and they won't know which one until they open up my car. And then they said he isn't sure if my sub will work. So I don't exactly know what to do. Any ideas? Maybe something cheap and something I could possibly do myself(not a requirement)? Just need some ideas.