What maker of WD hitch with sway control?

At what point do you not need a WD hitch? I have a 21' Camplite 21BHS Travel Trailer (3499 dry weight, 5000 lb GVWR). My TV is a 2009 Ram 1500. When I lower the trailer onto the hitch ball (no WD hitch), the truck squats about an inch and the trailer ends up level. The trailer has tandem axles. I haven't towed it too far yet, but I have driven down the Interstate at 65 MPH, been passed by trucks, etc, and no trailer sway. The biggest thing I've noticed is a bit of bouncing when I hit a patch of rough road, but other than that, the truck handles great. We've taken it on one 60 mile trip to camp to test the camper, and it towed great. Even though we experienced no sway, should I have a WD hitch or anti-sway bars? Eventually we want to increase the distance, and for our 30th anniversary in Sept 2014, would like to return to Arizona with it. Before I make a long trip, I want to make sure we are properly equipped, so any input is greatly appreciated.

Thanks,

Doug