In previous posts the advice I was given was to use Extruded Polystyrene Insulation in my basement walls.

I see at the big orange box store they have 3/4 -2x8 FOAMULAR Extruded Polystyrene Insulation with an r value 0f 3.8. Can I double this up to give me more insulation and r value or or is there no extra value in place two sheets between the wall studs?

They also have 1 1/2 FOAMULAT INSULPINK extruded polystyrene on sale, but Im not sure what the difference is between the two products and if this is exactly what products were that you guys advised me to get.