I'd recommend you replace your cable boxes with an HTPC installed with a cablecard ready device. A Ceton InfiniTV4, which is what I use, for example, would allow you to record up to four programs simultaneously or record three programs while watching a fourth. Your storage space is only limited by the hard drives you install into the HTPC.
-Wolf sends
Edit: Oh. and it's just one coax cable connection to the TV Tuner Card.