Given your willingness to consider a second HDHR, it sounds like you may want to build a system that terminates a fixed aim antenna on one and a rotatable antenna on the second.
I would use a 2-bay UHF antenna such as the Antennas Direct DB2e facing south and slightly east (fine tune the aim using the signal metering of the HDHR). I would not use a preamp if you're only connecting one tuner using less than 50' of RG-6.
I see no low-VHF on the air or pending, so the HD7698P on a rotator would be a very good choice for going after the more distant signals. Terminate this antenna in the second HDHR.
http://forum.tvfool.com/showthread.php?t=820