CAA: Christian Anime Alliance

I'm not sure if I have a junky router or if it's my house, but I can't get reception from more than 30 feet away from the router. We have a linksys Wireless - G Braodband Router (model WRT54G). I don't really know enought about all of this to know if it makes a difference, but any help is appreciated. Also, if it matters, I'm trying to use it to play Mario Kart DS on the Nintendo WFC.

Are there any walls in the way? Also microwaves and flourewscent lights and some cordless phones also operate on the 2.4ghz level, which can cause interference.

An extended antenna or a range extender box are suggestions from Linksys

What's the price range looking like on those? Also, what kind of range extension would they give?