Your 20' report is very good. I see little if any advantage to mounting at 40'. A premium system would consist of two separate antennas.
Fist, an RCA ANT-751 pointed toward 86° compass. Simply run that to your TV, no amplifier needed, even if you split to several TVs. (Unneeded amplification is often a source of trouble.)
Second, a Winegard HD7694P pointed toward 149° compass would give you signals from the US. For a single TV, I don't think you will need amplification. This antenna would need to cable to the TV(s) separate of the first antenna. To connect to the TV(s), you have several options,
http://forum.tvfool.com/showthread.php?t=2882.
If you are inclined to use HTPC technology there are even more options,
http://forum.tvfool.com/showthread.php?t=820