I'm a bit surprised seeing that TV tuners for PC with decryption support are so rare in the US, when "comparable" DVB tuners with CI/CAM-modules are reasonably cheap and widely available in Europe.
Is it simply that the early generation of PVRs like TiVo and their ilk never got traction here (and in many countries the cable/satellite providers where dog slow introducing their options too), so that when signals started transitioning to DVB from analog there was a pent up demand for DYI/flexible solutions that was/is not present in the US?
While there is a lot of hardware available, most of it either only supports free-to-air, or requires multiple components that all have to work together.
You need to set up a card server for each channel you want to watch/record at the same time (there are some hacks, but they're unreliable). You need a decryption module for each card, and there's only one that actually works for most providers (many others might work for the current encryption used by the provider, but they tend to tweak that regularly). You need one or more tuner cards to get the amount of channels you want. And a bunch of cryptic software to make them all work together.
Most of the general and free software available are MythTV plugins or modules (which works, but requires some fiddling to set up), and most of the rest is part of a commercial solution. Which have a strict list of supported devices, providers and locations.
Of course there are all-in-one solutions, but most I looked at had some major setbacks, mostly in the support available for your specific source and provider, and for Windows Media Center. But they can work rather well in combination with (a subscription to) commercial software, if it supports that specific setup and provides the things you want.
If you use a DVB-C (cable), it isn't supported by Windows Media Center, and so the producers supply hacks that make it think it's actually a DVB-S (satellite). Unfortunately, the channels used don't match, and they're not in the provider database, so you have to set them up manually. And they tend to reset. I would really not recommend trying to use this. It might work, but more often it does not.
There are some all-in-one USB solutions, which mostly work if you use the supplied viewing software (or a MythTV plugin, if available), which often doesn't support recording very well, if at all. And they only tend to work with WMC as long as they're DVB-S and the provider and location are in the database.
So, it's hard to give an overall best solution without knowing the details, but overall a MythTV derivative is your best bet, and VERY convenient to use if you don't mind using a Linux box.
