I had a similar problem - signal degraded by metal joists in between first and second floor.

So I got a Netgear Wireless powerline range extender kit:
http://www.netgear.com/Products/Powe...s/WGXB102.aspx

One of the doohickeys gets connected to your router via ethernet, then plugged into a nearby wall socket. The other doohickey gets plugged into a wall socket somewhere else in your house, and acts as a wireless repeater.

No setup if you have a netgear router.

Very cool.