Any wireless n router will have more than enough range for your house - if not half your street!
Even Wireless N is slow though (around 90Mbps in real life) and only runs at the speed of the slowest device on the network. If a G device connects to ur network the network speed will drop to less than 54Mbps, and if a B device connects it will drop to 11Mbps.
U might want to consider getting some AV powerline home plugs - to extend ur network using ur existing mains supply.
I setup a network for my mother - with 2x 1Gb powerline adaptors. One plugs into the router in the bedroom and the other one into a gigabit hub in the livingroom, allowing devices in the living room to connect to the network without another phone line.
As long as u get the AV (200Mbps) or AV2(1Gbps) spec they work really well - more than fast enough to stream blu-ray quality over a network. And so easy to setup a trained monkey could do it.
About £70 for a pair of 1Gbps plugs. DO NOT get the 14Mbps or 85Mbps ones !