Basically all my amp experience comes from a lab for a company that made routers at the time. So I can't screendrop anything for you. To answer your question though, yes additional noise can be a problem but the first problem you'll hit is the wall. Wifi is pretty fickle and line-of-site is still king. With a yagi or just a directional antenna (you guys probally already know this) the difference between a connection two miles away and 100 feet away is purely what objects are between it. So walls even above 10 watts is going to stop much of the signal from reaching the amp, card, radio. It's why we all end up with antennas near windows. But with signal strength what you will find a problem with is overloading clients connecting to you. Operating at 10 watts in the cage but with the door open would cause the floor directly below us to give a -0dBm reading for that AP. That laptop could still see other ssids around the office it just wasn't able to connect to any of them. Walking 15 feet or so away let the signal drop enough to connect again but that floors IT thought that their repeaters were not strong enough to reach that area, not that they were technically in the eye of a radio signal storm. The fact that 15 feet and some brick and concrete was the difference between someone connecting and not connecting to a completely different ap gives you some idea of how much signal bounces around. Real world problems you'll find with no-name ebay amps is overheating. Rarely do any I've seen come with anything designed to vent and keep them cool. Different cards react differently, but the end result of locking up and ssids disappearing is pretty much always the same. You'll also find that the generic cables that come with the amps (rp-sma female to male that link the amp) will melt apart over time. So anything above 2 watts starts to require thicker coaxial cables. In the end, I've gotten more active access points from being 20 stories up without an amplifier, but again line-of-site is everything. Also we were forbidden to take any of the equipment out of the lab, so testing elsewhere wasn't possible.