Help connecting two wireless routers wirelessly to share one net connection

Here is my setup. I live in an apartment that was initially designed as retirement living for seniors. This is important as the walls are extremely dense to keep out sounds from adjacent neighbors. My other issue is that my DSL modem is on the second floor (and cannot be moved without spending $$$) and I primarily work downstairs via my wireless connection. With the walls and floors being so incredibly dense, my connection is weak and I get frequent disconnects and erratic speeds.

Here is what I want to do. Upstairs I have a Linksys WRT300N attached to the DSL modem. This modem is using the most current Linksys firmware and has AES security on as well as all the information for my static IP (the DSL modem is setup as a bridge, so my 300n handles all the IP stuff). Directly below the 300N, on the first floor I would like to have my WRT54G v6 using the DD-WRT firmware connect to the 300N wirelessly and then onto the Net. I cannot run any cable to the downstairs being its an apartment, so I would have to do this wirelessly. Then when I am downstairs working, I can either use the wireless of the 54G to connect to the net or a wired connection.

My laptop's wireless card/USB card are both a/b/g units, not N.

Is this doable? If so, what do I need to do? I wish I could do a wired network as there are so many other wireless networks in my immediate area (14 to be exact), but no conduit that I can work with.

 

Something like this might work for you.

http://www.dlink.com/products/?sec=1&pid=533

 

Yeah, I have been thinking of looking into the powerline networking items, but I am hoping there is something I can do with what I have.