How can you transfer your whole gamer profile & downloaded content to a different hard-drive (Xbox)?

This weekend I am picking up a new Xbox360 slim, and I want ALL of my current memory on the other xbox. At the moment, I am sharing my Xbox, and I want to move my gamer profile and all it's data onto the other hard drive, because there are other profiles on the one I have now, so I can't just take the hard-drive. I know that I can download my profile onto the other one, or put it on a USB drive, but I have a lot of downloaded content for my games on it, and last time I downloaded the gamer profile, the DLCs weren't there, so I downloaded it back onto my original white console, and put the whole harddrive into the other console and I could still not access my DLCs. Is there any way to move all my downloaded content to another harddrive with my profile?

The downloaded content is season pass for Black Ops 2, and Left4Dead2 Maps.