I've played around a bit with this and one thing that I think is easy to overlook is the directionality of antennas.

Not familiar with the N1, but before you leap into mutiple access points, extenders, repeaters, etc you might want to take a look at the documentation that came with the router.

Which way the antennas are pointing can make a difference.

I had a Belkin with two antennas and putting them perpendicular to each other helped.

And a Buffalo that I had, had no external antenna, but it turns out that it's actually just case with a PCMCIA wireless card on the inside. Rotating the thing changed signal strength in parts of the house.

(BTW, multiple routers/same newtwork ID can be a real pain. I tried and switched to other methods, but have vowed to go back and figure it out one day...)

-R