Here is a link to a Taiwan company that makes both digital cable and satellite PCI cards -
http://www.twinhan.com/english/english.htm , and they are quite cheap around $150 each, or atleast they used to be. They were selling them directly from their website, but now there is only a sales contact email... you might be able to get one from a European reseller, and they do offer them OEM for you smooth talkers. I have no idea if they would work with North American DirecTv/digital cable standards. I searched long and hard and found little info, outside of technical details I have yet had the time to decipher. One of their DS cards comes with a pcmcia common interface breakout, which fitted with a pcmcia smartcard reader might work in North America - if such a thing exists?
As far as DirectTv never allowing pci receivers to the general public... I was talking to a sales guy from DishNetwork at a tradeshow who was demo-ing a Linux box with a DS receiver card (strictly OEM) who said DirectTv (soon to be Dishnetwork... more later) once partnered with Gateway about 4 years ago, and sold to the public a package consisting of a pc with a DirecTv PCI receiver and a 32" (640*480 interlaced probably) display. It ended up being a huge failure. He didn't go into detail as the topic was just a sidebar, but I would suspect it was the image quality of a sub-par display.
DishNetwork owned by Hughes... and according to this guy, is in the process of buying DirectTv at which point current DirectTv customers would have to be "switched over eventually"- I make no claims to truth, after all he was in sales.
Anyway, I wish there was a DS receiver card for the US market that I knew worked with current providers. I'd buy it in a heartbeat if it were reasonably priced and I'd even pay the monthly service (really). Anything to get away from analog ntsc.