No worries on the confusion. The audiophile nomenclature doesn't help either. If it was all fundamental units and LaPlace transforms, it would make sense to me, but no one else...
Anyways, at 2Ohms, 1040wpc yields 116dB@20Hz and 113dB@15Hz, so there is what one would call a "noticeable" (3dB) gain at 15Hz. Worth it in my opinion, since sub20Hz output (extension?) is why I'm doing this.
Next is wood selection. My better half approved Duratex for the living room, so that seems the no-brainer. I haven't built a cabinet in 25 years, so its nice to know minor mistakes can be hidden.
I'm thinking of going plywood instead of mdf for sawdust and weight. If I cut my own handy panels from a 4x8 sheet, the cost is a wash. Plus, living in Florida, water is always a (minor) risk, but I think ply would survive incidental water contact better than MDF.