Setting up wireless router

At my current house, we have Apple Airport to provide wireless internet. I have my 1TB Western Digital hard drive plugged into the USB port of the Airport so anyone in the house can access it via the wireless network.

I'm moving into a new house where the internet is available in various rooms in the form of ethernet cables. I would like to set up a wireless router in my room (where there is an ethernet cable) so my girlfriend's computer, my computer and my PS3 can be simultaneously connected, while also having my external hard drive connected to the USB of the router.

I don't have direct access to the modem or the router it is already going through to distribute the internet to the various rooms. I've never really gotten my head around home networks, so I'm not sure if you can have a router connected to another router.

If it would help at all, I'd be able to have my PS3 and/or computer connected by wire, as they wouldn't be moving around much (the computer is an iMac), the wireless connection would be mainly for my girlfriends laptop (not sure on the specs, but it's running Windows Vista) and a work laptop that I occasionally have over (a pretty new MacBook Pro).

If all this is possible, do you have any suggestions for what I should look for in a router?

Cheers for your time!

-Richard