Joe you are on the right track to figure out the range thing....I have a nearby outdoor system at a yacht club, using 3 sector amplified antennas driven by Buffalo (residential) access points....I will be testing shortly using Orinoco card and Fab-Corp. 5 dBi mag antenna; will also get details on amps they are using

as for the FCC, i would guess they'd have rules on stuff like not-to-exceed saturation flux density for amplified, unlicensed 802.11; obviously the power and proximity of abundant unlicensed 802.11 is Sirius' big concern for interference with their expensive licensed satellite radio service

so the FCC is likely to have metrics like SFD with to regulate the unlicensed bands; although it may be difficult for you to determine the SFD of an amplified system without the right measurement devices, you can probably estimate your system's power using formulas taking wattage, antenna gain, etc. into account....the wireless consulting guys do this stuff for breakfast (usually for a fee, of course)