Maybe nobody knows?
But I think that the transistor count increase in the MX series would be no more that the Gf3->Gf4 increase of 6 million. Gf2mx -> Gf4mx gained more transistors dedicated to AA than Gf3 -> Gf4 (since the Gf3 allready had HW AA), but on the other hand the Gf4 got something completely new, dual display suport, wich the mx allready had partial support for. And I don't think the MX got an extra T&L unit.
I can't quite remember how many transisters the gf2 mx had, but I think it was less than 20 million, so I would guess that the Gf4mx has about 20-22 million transistors.
Pure speculations, nothing you haven't allready thought of youself, I guess :smile: