hey one night a few weeks ago i took 24mg of valium before heading out. Met up with some friends to have a few drinks. Because of my valium intake, i become nicely drunk from less drinks than it would normally take.
Later on i ended up dropping a pill. I don't know if it was from the valium or a good pill, but i experienced euphoria and was "loved-up" for the first time in AGES (having just broken my weekly pill bingeing habit)
Having said that though, I'd always thought that valium would not increase the effects of MDMA, and thought it best to assist comedowns. Also, i consumed the valium several hours before dropping.
So basically from my experience i think that combining valium with E won't lessen your roll (probably so if taken at the same time however.) but i don't know about enhancing it. I put it down to a good pill!
But do a search on it anyway, to find out the facts on combining the 2 drugs.