Looking for a Wireless N Dual Band Router with good signal coverage

I have bought a Dlink DIR-855 N Gigabit Quadband Wireless Router for my home after reading lots of reviews. But unfortunately it is having very less wireless signal coverage. I placed it just one floor above and only getting poor signal downstairs. I got the RMA to return it back and have to find another one soon.

Could you suggest a N Gigabit Dual Band Wireless Router which has a good coverage. I read about Netgear WNDR3700, LinkSys e3000, Draytek etc. But before zeroing in on something, I prefer to get some feedback from people who really used or have exposure to one of these.