I love ya saint19 but....
Yes you will see an improvement when running RAM in dual-mode and not single-mode.
It's not enough to make you scream and jump but your system will thank you by being more responsive...
Then the other benefits are obvious like the extra slots available and less heat (not enough to mention but hey, why not..)
If you have all the RAM then run test yourself, I have done this myself a few times when upgrading and have seen the difference.
Even though the WEI assessment is kind of bogus, run it with the RAM in single-mode then run it again in dual-mode.