Hey ZxRO - I think the best options for what you are intending are as follows:
1. A Hauppauge HD-PVR. Using component video cables you can record up to 1080i with this device for most channels regardless of encryption on HDMI since the component cables bypass the HDCP snafu. No HDMI-in for this one.
2. A Hauppauge WinTV DCR-2650. Using a CableCard (which I've heard the first CableCard for most areas of Comcast comes at no extra monthly charge) you can record any unencrypted channel on Comcast. In most areas Comcast only encrypts premium channels (HBO, Showtime, et cetera) and Pay-Per-View shows, but you might want to double-check that before considering this item. Anything channel Comcast does not mark as copy-once via HDCP can be recorded and viewed at any time. (If it is encrypted then you can watch it again but only on the PC on which it was recorded and only if you do not ever change the hardware of that PC.)
3. A BlackMagic Design Intensity Shuttle. I would double-check the system requirements for this one as you have to have some pretty up-to-date components in your PC to get this box to work (and some patience during the installation process), but this one also can record via component cables, which, as stated above, avoids the HDCP headache. This one also has HDMI-in, which again will work for any unencrypted channels.
4. An AVerMedia AVerTV USB HD DVR. Somewhat similar to the Hauppauge HD-PVR but less expensive.
I wish you great success in your search!