To answer my own questions; I found an installer with an M-Card. Now my TivoHD is up an running. The sales guy wasn't sure, but I scheduled an installation for Friday. I got a call on Friday from the installer saying he didn't have any cable cards and had to postpone to Saturday. A different installer showed up also didn't think he had any cable cards, but found one S-Card in his truck. We got that working. I scheduled for another guy to come back out with another card, and he had an M-Card. Now, everything is working great!