I have some 'Genius' speakers at the moment, And I'm sure several consumer level (not studio level) speakers say 20Hz-20kHz on them, but perhaps they don't bother with the flat response patterns as you suggested Hugh!
My moral issue with the sub, is that I hold the theory of 'not everyone has decent speakers, let alone a sub' to my chest very closely!
I'm also looking at monitors and the reviews say things like, 'speaker sound quality is not loud enough or of good quality' - so therefore, not only are they not 'in-the-know' of what a 1w pair of speakers in an LCD monitor should produce, they obviously don't use a sub! Or consider a sub!
I don't do much for clubs either, so I feel a sub would be wasted!
Cheers for the responses anyway, I'm sure I'll be happy with them =D