The decoder essentially lets you display video without taking much CPU. However, the drivers weren't entirely there back in February or so. They've come a long way and I'm going to try them again. I had bought a NVidia card to do the display out in the meantime. I think the PVR's display is cleaner.

I only have the one capture card. PVRs are really the only way to go if you want more than one capture card and want to watch TV as well, as the CPU usage will be minimal. Just be aware that there can be stability issues.

Don't use a VIA chipset mobo either. I don't know about NVidia chipset mobos.

Be warned: this is NOT an easy project. If you're not comfortable fiddling kernel and module settings, endlessly recompiling things, and generally mucking about with the innards, you won't like doing this at all.

That said, KnoppMyth is supposed to solve all of that. I Haven't Tried KnoppMyth (I rolled my own with Debian). I'll let you know in a month or so when I get the time, though. :-)

Start reading the mailing list for a while to get a feel for what the better configurations are. I haven't been keeping up; it's very high traffic.