I use an Airport Express to extend the wireless range and signal strength of my Airport Extreme as my house is "range-challenged". My current set-up has the Extreme (base unit) downstairs and the first (Express) unit upstairs. Two questions: (1) can I use a second Airport Express unit (further away upstairs) to further extend the wireless range amd signal strength in my house? (2) if I do add the second Airport Express, is the wireless signal extended from the Airport Extreme (base unit downstairs) or from the (first) Airport Express unit (upstairs? Or from both the Extreme and first Express? Hope this makes sense Thanks!