Good quality consumer grade modulators are only capable of a certain level of performance. Until you are willing to pay for the precision tuned commercial grade filters that would limit the output of the modulator to a single channels bandwidth, expect consumer grade modulators to emit RF on adjacent channels above and below the channel they're set to operate on.
This often means that a consumer grade modulator can interfere with reception of OTA channels. Simply turn the modulators off to test for interference form them. If you have interference originating from a modulator, try setting it to operate on a different channel.
Amplifiers compound this trouble because they can mix RF signals together, which produces interference on frequencies up and down the RF spectrum. Use no more amplification than needed, none being an ideal target if at all possible. To that end, a high gain antenna may secure enough signal power from the air to reduce or even eliminate the need for amplification.
For what it's worth, the OnQ Video Engine specifications for noise performance are quite poor compared to current competing distribution amplifiers. The OnQ was spec'd at 7 dB NF as compared to the Channel Master CM-341X series spec'd at 3 dB NF.
With signals coming at you from many directions, I'm curious if you would entertain the idea of using Home Theater PC technology and network attached tuners? The solution is complex and therefor not for everyone. But you would get a premium performance system that maximizes your reception capability.
http://forum.tvfool.com/showthread.php?t=820
Last but not least, you have an ally in the FCC,
http://www.fcc.gov/guides/over-air-r...n-devices-rule. They preempt the HOA and local governments that would try to tell you you can't have a TV antenna.