Kind of depends on how heavy the streamer was. The motions for casting a heavy fly are a little different. Some folks call it "chuck and duck". Just play with it a while until you're comfortable.

On another note, 5x for a heavy #6 streamer on a 6 wt rod seems awfully light. Bumping that up a couple sizes, and shortening the leader if possible will help a little bit on the business end.