P.S. The RRP for the Screen Technics 100" Fixed I mentioned earlier is old and was updated a couple of months ago (sorry, bad memory day). It is currently $819 (again, that's the full RRP) - which is still a lot less than $1200. If someone is asking $1200 for a Screen Technics 100" Fixed - in Matt White - then they are ripping people off.
That said, the RRP for a Screen Technics 115" Fixed is $1209 (the price jumps very sharply once they get above 110").
I say stick with Matt White. The Matrix White option adds somewhere from 50% to 80% of the price again on top (so a 100" goes from $819 to $1359), and I've always felt using special coatings etc. on the screen had the potential for side-effects like increased chance of hot-spotting or having an effect on the colour (shifting colours/tints away from natural). Today's projectors are more than capable of producing a bright, sharp, high contrast image on a standard Matt White screen - I reckon you're better of getting Matt White and use the saving somewhere else.