Not quite what I was getting at for priority (but stick with me because the short answer is yes).
For each recording, you can set which channel you want it recorded on. That can be any channel, channel x, channel y, HD preferred, HD only, SD preferred, or SD only. I generally use "HD Preferred" in which case Media Center will always attempt to record the HD signal unless it's not available and then swap down to the SD signal.
What you're referring to is called "sources" in MC7. For each channel, you can define the prioritized sources for each channel. Say for example you set up WGRZ in Buffalo, you can set the primary source for that to be the HD tuner you have pointed towards Buffalo. You configure sources in the guide setup.