Well if you do decide to change your mind about wireless, you can purchase a wireless switch and hook your A/V equipment up to that switch with Cat5... and then the switch will communicate wirelessly with your router at the computer. It would be a simple, effective, and inexpensive solution.
The "cheapest" solution is to stick with what you use now, or to download the updates from your computer and burn it to a CD (or some are compatible with flash drives), but that's kind of a pain to do.
If you want convenience, and are still adamant against wireless, you can either run new CAT5 cables, or use a coax solution like you posted.
Since money's not the issue here, then it's pretty obvious what your best solution is...