Because you are already using some form of HTPC technology and are considering the CM-7000PAL, take a look at
http://forum.tvfool.com/showthread.php?t=820
Network attached tuners make multiple antenna systems far more flexible and useful than was possible when passive RF combiners were the only choice for merging two or more antennas. If you are trying to simultaneously access Boston and Providence stations an option would be to install an antenna dedicated to each market. HTPC technology is built in to Win-7 Home Premium giving you full PVR capability in addition to basic live TV viewing features. If you are inclined toward Linux, MythTV is a well developed and supported open source Media Center software suite... that's free.