I've ordered a DVB card. It's the Hauppauge WinTV-Nova-t PCI. Hopefully I'll be able to set it up on Linux and integrate it with the MythTV setup.
It'll hopefully allow me to record MPEG2 streams without recompressing, as well as allow me to record two things at once in MythTV.
I'll post my progress with this card as I try to get it to work.