^What suss said.
But also, you don't need to take out the center headrest - just the side two. You might also need to move the front seats forward to get the seat base to go forward enough to get the seats down all the way. As suss said, the seats will be flat, but the trunk area would be higher if you have the full-size spare.
2012 FF Ti HB Kona Blue, DCT, Built 5/24/2011, 401A + Ti Handling Package, Parking Technology Package, Winter Package, Moonroof, and MFT w/NAV at v3.6 124k miles and counting...