bridge between two airport extremes?

I need ethernet access in a spot of the apartment that does not have a network socket. It also happens to be close to a weak spot on my wireless network. Normally to get network there I would use an old base station with dd-wrt as a wireless bridge, problem is I would now prefer better performance (and limit amount of .g hosts on my wireless).

My current set up:

- Airport Extreme (.n) in a switching cabinet in my hallway
- 100/100 internet via ethernet in the wan port
- gigabit lan in other ports
- Wireless getting close to 10MB/s internet speeds with macs that support .n networks

I know I can extend my wireless by adding another Airport Extreme, but how much would this slow the speeds (I would imagine it has some effect)?

Could I also bridge the connection to the ethernet ports of this second Airport extreme to get an ethernet connection to my media player?