First, you need to rethink what you're asking. Your HTPC is another component in the home theater system and should never be mistaken for a controller. They do not have the input or switching capabilities to do what you want nor are there any aftermarket add-ons for a PC that will enable this feature..
That being said, what you need is an HDMI switch that you can connect everything to, including the HTPC. The only caveat is whether or not all of your components use HDMI or DVI as the video output. If any of them use DVI then you'll have to find a way to switch the audio independently of the video. There are HDMI switches available that have separate audio inputs that can switch both simultaneously.
My next question is, why do you have a Cox HD DVR when you own a Tivo HD? Dump that piece of crap and get another Tivo HD or wait until the Ceton tuners become available and replace both DVRs.
My third question is, why do you have a separate Blu-Ray player when you already have a PS-3? If you really want to make your life easier and have less clutter in your setup, here's what I suggest.
1. Get the Ceton cablecard tuner when it becomes available. This will allow you to get rid of both standalone DVRs and eliminate all of the monthly fees associated with them. You'll only need a single M-card with the Ceton tuner card.
2. Get a BD-ROM drive for your HTPC. This will allow you to get rid of the standalone BD player.
3. I am assuming that your OTA HD is by virtue of an ATSC tuner card inside of your HTPC. If not, get one and eliminate yet another piece of external hardware.
After doing all of the above, you'll only need to switch between the HTPC and the PS-3 and still have all the same functionality as before. Before you restate that you already have the other hardware I have just one more thing to add - sell 'em on ebay.
