I use an HTPC with a Hauppauge HVR 2250. It has dual ATSC tuners, so it can record two shows at once or record one show while watching another. I also use my HTPC as the media server so that I can watch shows on my gaming PC while exercising (it's an office/exercise room), and my wife can potentially watch them on her laptop (although streaming HD wirelessly probably won't work too well).
An HTPC would eliminate the requirement for ATSC tuners on your TVs, because the HTPC would connect via HDMI (or DVI to HDMI). However, I'm not certain what you would do for all three TVs. I'm not sure if there are converter boxes that output HD, but that might be something to look for. Some people use an HTPC connected to one TV as the media server and then use media extenders connected to the other TVs, but that's a lot of extra expense unless you already own devices that can be used as media extenders (i.e. XBOX 360).