The MX are the new Keplers to replace the older Fermi lefovers they rebanded from the GTX 5XXm series.
I should have one the the Asus GTX 675MX's soon to test out but no word on if its wired up for the current G75's like the VW but it is a MXM card but the guy who's sending it to me had no way to check if it was the Asus proprietary pin out.
But the new i7 3630QM people wont see any diff with the extra 100mhz they added on it. You can get that out of a BLCK raise with the 3610qm.
But As soon as i get the card i'll be testing it out in a current G75VW and see if it uses a new cooling system or if the one from the GTX 660m or the GTX 670m will work.
But performance of the GTX 670MX should be on par or slightly faster then a GTX 675m so it should be a nice card and if the thing overclocks like my 660m then there is a very nice alternative to the GTX 680m