RCA Scenium & Comcast Digital Cable?

I am currently getting analog comcast cable, just the standard
cable...channels 2-23 right now, but was considering upgrading to digital
cable.  There is a trap on my line that blocks the higher channels, although
the ones in the 90's pass through the trap, but come in scrambled, because I
do not subscribe to them and do not have a cable box.

I am ordering an RCA Scenium TV with QAM next month.  If I wait until I get
the new tv, can I get digital cable (unscrambled stuff) w/o having to sit
another box on top of the tv?  I realize that I'd have to pay comcast extra
money each month if i want all the movie channels and such, but I just want
the High-def channels, which I can only get with digital cable.  I'm not
interested in getting the HBO and Showtime HD channels, or any other
"premium" HD channels, such as the HD PPV channels....I just want my local
channels and ESPN and Discovery if I can get them.

Comcast is telling me that I need to rent their set-top box regardless of
what type of tv I have.  That is exactly what I DON"T want to do and is the
reason I'm willing to spend extra money to get the digital TV.  I don't want
to pay any monthly rental fee and/or have a set top box on top of the TV.

Will the Scenium do the trick or am I SOL?

Many thanks.