IMO, Lowering and duals are really appearance mods (Although you may gain 5rwhp from the duals). I think a lowered V6 with that wimpy turned down tip looks as bad as a V6 with a flashy body kit and stock 15" wheels.
The Duals is a nice place to start with performance mods, and arguably is necessary if you are going to do anything to the engine.
So my 'vote' would be for duals.
Can't afford Mods? Go To College!