I should think that since routers fall under the FCC's part 15 unlicensed devices certification, the power would be strictly limited, probably to 100 miliwatts. So, to improve range you can either make a much more sensative receiver or improve antennas.
If you use a singel router for several devices which are in different directions from the router, than a better antenna on the router is a bad idea as better antennas mean more directions. A directional antenna on the computer at the remote location does make sense as you want as much of its signal to be pointed at the router as you can get. I've heard, third or fourth hand, that the pringals can antenna works well. tom
