I was wondering if anyone knows if the Pioneer AVH-P4400BH will fit in a way the flip down door is still usable? Also what double-din kit would I need to get it to fit into place?

 

Looks like it will depend on the mounting kit and how far back it sits.
When I had a D3 in my tC I actually had to take some of the back side of the door off with a dremel so it would clear the **** sticking out when I closed it.

 

I have a Pioneer AVH-P2300DVD in my 08 tC the door works great!

 

Nice. Where did you get the din mount thing at? I forget what it's called but it also blocks out the unnecessary gaps on the side for a cleaner look.