Not wrong. I've owned a Q700 with a Q800 mobo in it - in fact, I did the work myself. The Q800 mobo fits in the Q700 case with no modifications. It fits physically; its rear ports line up identically; it connects to the PSU with the same connector in the same place; it has the same number and mobo location of drive ribbon connectors (SCSI and floppy).
If a Q800 motherboard would fit in a Q650 case then it should also fit in a Q700/IIcx/IIci case. I have a Q700 motherboard in a IIvx case which is identical to the Q650 case, but before that I had it in my IIci case. I had to hack the back panel because some things don't line up exactly, but it did go in.
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