I need to extend the range of an Airport Extreme? I bought an Airport Extreme and need to extend it's reach. I currently own a TimeCapsule.  I believe the TimeCapsule also has the wifi creating capabilities of the Airport Extreme.  Can I hook up my TimeCapsule to my modem and use my Extreme as an extender? If not, can I buy an Airport Express to do this?
You can use your extreme to extend your TC.  See the Apple doc here. http://support.apple.com/kb/HT4259