Is there any consensus on which underlayment is best for solid 3/4" hardwood? I'm installing 3.25" wide brazilian cherry. I am installing the hardwood in the upstairs of a bungalow. My basement is heated, but typically a couple degrees cooler than the upstairs, and less humidity.

Before I knew any better, the store I bought the hardwood at sold me wax paper. It sounds like Aquabar is a better product - I'm just not sure if it's worth the hassle of taking back what I already have and trying to find someone who carries Aquabar (I'm in Canada if that makes any difference). Plus, I'm probably in a fairly low risk scenario for cupping given that my climate is somewhat controlled below the floor.

Thoughts?

I usually use felt, but if I think there might be a slight moisture issue with the basement will use the Aquabar. Have never used wax.