You need to get a dual-link DVI switch (something akin, but not exactly, to what you just linked) to support the 2560x1600 resolution your computer outputs and the 1080p signal from HDMI. I would assume that a 30" monitor would be HDCP compliant.
A capture card is something very different from a display switch....
That looks like a pretty good design. For your cable system.
I'm using an EyeTV HDTV satellite receiver (a badged Digital Everywhere product called FireDTV-S2) with firewire interface to the Mac. Very good solution. I can use it with the MacPro and the MacBook Pro.
EyeTV has a fantastic GUI for recording and playback. The receiver has a remote that works very nicely with my Macs.