installing a kitchen island
If you secure the cabinets to each other, you should be OK. HOWEVER, how you do that is of the UTMOST importance.
You just can't attach them 'in the middle', just inside the cabinet. You'll need to attach them at the BOTTOM as well. Having just 1 'stress point' is not good. If you can defuse that to at least 2, possibly more, then do so. So when you DO attach them, attach them in multiple locations in the middle as well as 2 or 3 location underneath.
What I'd do is ctc the countertop installer for suggestions. Granite isn't as 'flexible' as laminate-finished countertops. As far as anchoring the countertops to the floor, I think it would be good. The movement may put undue stress on the stress points especially if it's moved a lot. Again, ctc the Installer. DEFINITELY secure the cabinets to the floor if you're running electrical to them. (Case Closed on that one.) You'll need special drill bit if you're drilling through granite and marble. Do some homework on this BEFORE you drill by researching some books out.
My best to ya and hope this helps.
Jay J -Moderator
PS: God Bless America!