Fitting a 6.5" speaker anywhere is easy, fitting the necessary enclosure for it to perform well in the lower octaves wouldn't be so easy. Given equal excursion possibilities (for my example here only), when changing cone diameters the enlcosure size requirement scales pretty linear.
So, imo, it would boil down to what size enclosure is required for these things to outperform your above-average front stage mid running IB. Or, will these are these designed to run IB in rear decks? Obviously that would be a big help, but would then make it impossible to mount them 'anywhere' in small enclosures.