By placing your RAM into dual channel mode, you have effectively doubled its bandwidth, meaning that twice as much data can be transferred at a given point in time.
There should, in theory, be a noticeable difference between single and dual channel mode. However, this depends on the application. For many programs, such as Office (Word, Excel, etc), there will be a slight difference but not as much as you will see with graphics editing or movie conversion.
What is your current WEI score for the memory component? Rerun the assessment and you should see an improvement in this value.