Roof or indoor antennna and which one?



Hi, I'm sorry I'm not registered, I tried but the page keeps hanging but I'd appreciate any help you folks can give me anyway.

I'm looking at ditching Comcast but am concerned about reception. I have a tivo box with a cable card (but the card will have to go when Comcast does so I don't know how much good the Tivo will do me after that). The TV is a fairly new Samsung LN32D450G. I don't care about HD as much as clear reception. I only watch a few stations but they're ranging from green to grey according to TVFool's site, and here's the link they gave me:

TV Fool

I guessed at the '25 feet high' because I'm on the 3rd floor of a 4 story building. There are windows to the north that face an airwell, there is an indoor wall on one side and the rest are outside walls. The building was built in 1897 so is wood and has no insulation but I'm betting at least several coats of lead paint (lol!) I can mount an antennae on the roof if I need to.

I'd rather not spend a ton on an antenna but if it got around $100 or more it would be ok since it's still way cheaper than a Comcast bill.

Anyway, any direction or help you can offer would be great. There's almost too much info out there and it's confusing!