It's true the X2 is weak compared to the Smarty for power output in the low end. It does come alive in the higher end, but still pretty conservative. The Smarty fuels a lot harder down low.
By design, pressure boxes won't make much smoke. The added pressure helps the fuel to atomize and combust more completely, which means that even though you are adding fuel you're able to burn it more efficiently.
From what I've observed with my truck, when running a full load of Smarty, I can turn the pressure box up to clear the smoke faster and to add more middle and top end to the Smarty tune.
Keep the X2 and stack it with a Smarty using the the pressure tune. You'll know you have it then.