The DB4 will
probably work. It's not nominally designed for channels 7-13, but most of the channels in that band available to you are very strong. It might not have enough gain for reliable reception of WVNY, the US ABC affiliate broadcasting on ch. 13. My hesitation iscomes from not checking the beamwidth (sector where the antenna is sensitive) of the DB4. You have about 100 degress separating your Canadian locals from most of the US stations, and many antennas cannot "see" over that wide a spread.
A premium "set-and-forget" solution would be an Antennas Direct C5 aimed at 225 degress (magnetic). It's primarily a VHF antenna, but has very modest gain over a wide beamwidth for UHF channels, which is precisely what you need.
Unless you're going to have over 50 feet of coax between antenna and TV, you should not need a pre-amp. If you were to check the signal strengths reported by your TV without one installed versus strengths reported with the pre-amp installed, you'll probably notice an increase. However, this increase buys you nothing, as the background noise has also been equally amplified. DTV reception is all about signal-to-noise ratio, not just signal power.
If you haven't already, I would check our recommendations against a community of Canadian OTA folks at
Digital Home. In the reception results sub-forum, there are threads for every TV market. Post your query there.