TV Tuner Cards and DTAs

I have Comcast as my cable provider, and I recently got some DTAs from them. And I was planning on getting a TV tuner card. But I want to receive the channels I pay for, and not just local ones.

So my question is will I be able to view and record programs with a TV tuner connected to a DTA? I think it will work but I'd like to make sure first. If it won't work what will I need for it to work?

EDIT: What I'm basically asking is if it would be possible to replace the STB with a DTA. But, I don't think it will work since the DTA doesn't do decryption... does it?