Trouble getting wireless signal on far side of house

I'm looking for some help in improving my wireless home network.  I have a coverage problem with my Netgear WGR614 because I have a large home.  The Netgear is hooked up to a cable modem and works fine if I'm on that side of the house but on the other side of the house, the signal is weak or non-existent.  About 6 months ago I bought this Netgear device that plugs into the electricity outlet on the far end of the house and the other end plugs into the router and into a wall outlet there.  It worked okay for about 1 month but then the signal was freezing a lot and became unreliable so I quit using it.  I know there are some newer wireless routers out that I might should upgrade to but I'd like someone to suggest which one.  Also, should I try some type of relay or signal booster on the other side of the house or would it be better just to buy a super wide range router?

Looking for best ways to set up the home and specifically what products to buy at Comp USA or Best Buy, etc.

-Thanks, Jason