I don't know offhand, as my accountant (spouse) pays all the bills.

I do
know, however, that adding HD only increased my cable bill by $5 per month. I
already had Comcast digital cable with HBO. Interestingly, the new cable box
that Comcast installed for HD is also a cable modem (looking at your email
address if you use Comcast for internet perhaps you already have the
appropriate box). I've had Earthlink DSL for four years and it works well, so
I've never tried their cable internet service.
MW