I have to agree some of the older Linksys units would have better reception and throughput on marginal links when boosting their power to their max. However, cross channel interference also went up drastically when set past 80 mw.
The wl txpwr1 is the command to set the power. You will need the wl package.
txpwr1 Set tx power in in various units. Choose one of (default: dbm):
-d dbm units
-q quarter dbm units
-m milliwatt units
Can be combined with:
-o turn on override to disable regulatory and other limitations
Use wl txpwr -1 to restore defaults
Unless your in a really unpopulated area I would recommend an amp over boosting your Linksys and causing noise across the whole band:
http://www.provantage.com/hawking-techn … AUW02E.htm
But, I would always recommend a better antenna first. Directional panel antenna can produce great gains at reasonable costs. A 15dbi gain directional is WAY MORE gain than you will ever get out of amping your signal. Even a 15 dbi omni can be had for under $70 US. Unlike amps, antennas get a all of their gain without any distortion or noise generation in the signal, so maintaining maximum throughput is much easier this way.
Also, to get any benefit from an amp you need one at every radio. With a high gain antenna at just the access point, every connected client benefits with both transmit and receive gain.