Rice Burner

I currently have one 10" audiobahn sub in my T/A. I want to buy another one. What results will I see compared to 1 12" or 2 12" audiobahns? The 10 is run at 300rms at 2 ohms...it sounds good but it doesnt hit that hard...i think it is because of my box design? It is my first fiberglass box and i only used 2-3 layers of fiberglass mat. I dont feel it would hit as hard compared to if it was in a wooden box? advice? Thanks