Adding (older) used airport extreme to airport express

Hi. This is my first post but I often get so much great information from everyone here. Thank you!

I was just given an old airport extreme model #a1143 from the place I used to work. I currently use an airport express base station for itunes streaming and just added apple tv. I'm wondering how I can use this additional station. I have an office far away from the airport express that gets slower internet speed and wonder if I can use this to enhance the speed. I'm also receiving a pair of Audioengine a2 speakers tomorrow and would love to set up a remote wireless connection in the kitchen.

Any suggestions on how I can add this new-to-me airport extreme to my existing set-up. Is it any good?

Thank you.