40hz will be too peaky @around 50-52hz(rough guess) and WILL lack low-end and...therfore...will not be pleasing to listen, tuning at 32hz is the way to go, to have a wider frequency response so u could actually listen to the whole music but will not be as loud as tuning @40hz...
doesnt mean it wont be loud though!//content.invisioncic.com/y282845/emoticons/wink.gif.608e3ea05f1a9f98611af0861652f8fb.gif hehe
yeah. see how you like at first. after awhile maybe you can build a bigger box or tune it differently (depending on rf's specs cuz alot of their subs only like small enclosures).