HDTV PC Capture Solutions?

Akai asks: "With HDTV DVR's costing upwards of a thousand US dollars or more, I was looking for a HiDef capture card that would work with Linux and an external HD receiver. The pchdtv card looks nice but it's RF input only for HiDef content, and only supports OTA at this point. Both DirecTV and DishNetwork HD STBs can be hacked with FireWire ports, but it's not cheap, so I was trying to find a capture card with either DVI or Component inputs, or a converter to take either of those to FireWire. The old Dish Network model 5000 receivers had an option to output HDTV RF but they are no longer compatible with Dish's current HDTV broadcasts. Google has not been helpful in this regard, and all I've found is professional (>$2000US) format conversion gear. Is there a PC (hopefully Linux) based video capture solution that can capture the output of a cable of DBS STB (RGBA, DVI, or Component out) without a significant loss of image fidelity?"