I have a new double cab also. Here is what I went with and the logic I used.
I also went with an Undercover hard top
tonneau cover like the previous poster. It comes off very easy and is light (60 lbs) so one person can handle it, also locks well and makes me feel secure. Only problem is that I believe it only comes in black. The same cover is also sold under the Versacover name.
I went with a hard toyota bedliner. I think it gives you the best bed protection if you are throwing heavy objects (bricks) into the truck, cheapest also. Plus things slide out of the bed for unloading easily (lumber).
Finally to stop things from sliding around when I don't want them to (groceries) I bought a rubber bed mat.
Just my .02.