Sandy I was faced with a two floor issue about six months ago and happens to catch Invid's post at ars.
http://episteme.arstechnica.com/eve/forums...31#996006693831 I flashed the linksys GL with Tomato and it's been a good solution since. Personally, I run Netgear WGPS606 with a printer server that requires a biannual need to reboot. There are none of the reported heat issues, even running torrent, and the range is more than I need. (2 bars out of 4 at 150 feet. (any slowdowns seem to be Pipe related rather than in my network access point)
I thought the 3G suggestion was a bit overboard myself but I only pass um on, I don't make them.
With the return of the SnowBirds a friend with a large boat introduced me to a router that I was unfamiliar with.
http://www.draytek.com/product/Dual_Wan_Se...igor2910VGi.phpThe option package available on this router I've not seen from any other manufacturer. He explained the differences between professional grade routers and the type I use and the difference is remarkable. Not having a need for this level of equipment didn't deter my interest so as I was looking around at our local city annual Yard Sale event I happened upon one of these for $40 dollars.
http://www.netgear.com/Products/VPNandSSL/...rs/FWG114P.aspx To my surprise it has options that my WGPS could only hope for.
Netgear routers don't seem to have the same issues as Linksys, so the need to flash them with new firmware wouldn't have the same return. I don't even know if you could use DD-WRT on an Nedtgear?
Gunug your problem is becoming the predominate issue in the WiFi world, overlapping and saturation in housing complexes has caused many a disturbance throughout the radio wave community.
What were you able to do to restrict your perimeter while maintaining your local saturation?