It comes down to mass I would say. 2 Inch panels in the corners wont do anything for the lowend, probably more harm than good. I'd say a minimum of 6 inches of 703 or alike in all corners. Use the 2 inch for early reflections. I guarantee if you put 6 inch 703 in all corners the room will instantly sound more controlled in the low end. One thing people never mention though, It is important to like the sound of your room. Just because you fill all the corners and or make the room sound dead as hell doesn't mean it will be an enjoyable listening environment. I actually took down a lot of my thinner hi frequency absorbtion because the room didnt sound the way i liked.