Once again, our JW doctrinal background gives an unsuspected (yet powerful) ring to a NT passage, which was not prioritarily about heaven as a destination (and certainly not as compared to another destination, i.e. earth).
The Lukan version of the saying which substitutes "knowledge" (gnôsis) to "the kingdom" is particularly interesting in view of the parallels in the Gospel of Thomas (logia 39 and 102): notice the comical Greek topos about the dog in the cattle's manger.
http://www.earlychristianwritings.com/thomas/gospelthomas39.html
http://www.earlychristianwritings.com/thomas/gospelthomas102.html