If i put MPX and SPS speaker behind acoustically transparent screen, sound quality would be the same as locating infront of projector screen ?

No, but it would be the same as ANY speaker placed behind a transparent screen. Whatever the particular screen does to the sound waves will affect all speakers the same way.

Which I guess is another way of saying that there's nothing like a true acoustically "transparent" screen. Any material that has to permit very little light to pass through it (and reflect it instead), will be challenged to allow sound to pass through unaltered, even allowing for the large differences in wavelengths between light & sound.

Which is not to say that the benefits of an A/T screen do not outweigh the compromises, most significantly being able to mount the center channel at the correct height, as opposed to typically a few feet above or below ear-level. This is even more crucial now that height is a major factor in the new 3-D sound formats. Of course, the popularity of A/T screens was driven more by aesthetics than by sound quality, and that is an important factor to consider as well.

Will the MPX be used for your surround channels? Hopefully, not for the Center Channel. Which is not to say it won't make a fine center-channel speaker, but a 3rd SPS mounted vertically would be the better choice. IMO, of course.

In my experience the acoustic weaves have by far the least affect on the sound (SI's are the best), but are not favored by videophiles because their non-smooth surface does soften the video a tad.