Get yourself something like 1/2' PVC pipe and run all the cables through it. Then get yourself a couple hundred feet of twine and run through it. Now, when your Cat6 goes bad, or in 5 years when we all start to upgrade to fiber or something else new, you can run cable with no hassle.
Good idea. To add to that, if you're opening the walls, take photos of the studs, electrical lines, and any other obstructions in the wall, so that in the future, if you want to run some new line that doesn't fit in your conduit, you'll know what you're drilling (or more importantly, not drilling) into.