I have a Netgear 824m (combined wireless access point, router and modem) I would recommend Netgear, as they are a very reasonable price and provide excellent support. Setting up is very quick as well. I know one of my friends uses the same product. He has his plumbed into a phoneline upstairs while his computer is connected in the office downstairs. He also is able to plug his laptop in as required.
Try click here for a few reviews of products. I paid £120 including a wireless access point for mine. Have a look at the different wireless standards. Walls affect the performance (Although from personal experience B seems more than adequate to get through walls without dropping speed) There is the WGT624, with is G standard (also compatible with B) loaded with security features, with hi potential speeds. Its about £100, plus access cards (depends which ones you choose to the cost)
I went for the all in one option as it makes a nice compact option without too many wires all over the place.