You are right - they apparently have a different bass driver and a big ugly foot on the bottom.
The problem with the IQ 5 SE's for a lot of folks would be the stability. It has such a small footprint that a toddler could easily knock it over. I can only imaging the IQ7 and IQ9 are worse in this regard.
I will now be on the lookout for some bargain IQ7's or IQ9's as the stability thing does not worry me.
NAD 515BEE, NAD C325BEE, KEF IQ5SE's, Silver anniversary XT, Chord Crimson interconnects.
Panasonic TX32-LZD80 and DMR-EX77EB