^^^maybe coz as i said your deviced(maybe) are not using the N signal.
Even i got a N series router but if you look at my devices laptop(G), iPod (G), Nokia N85 (G), Nokia C7(N) and SE xperia arc(i think N but sucks the most) not all use the "N" signal.
@abhadi try changing the position of the router to a more central and higher position before indulging in a new one.