AT screens really diminish picture quality?

Their 4K material should perform closely to the Enlightor 4K material. If you want an AT fabric with the least amount of visible texture or visible holes this is one of the best (and only) options. Is there a reason in particular you want to go with a curved screen?

The only big benefit is more light gets reflected back towards the viewer (instead of reflecting on to the walls) and if you're using a curved screen with an anamorphic lens in a 2.35:1 scenario, if the lens is creating a pin cushion effect the curvature of the screen helps reduce any noticeable pincushion because it conforms to the artifact.

There really is no PQ benefit to using a curved screen. It's really a matter of what you like to look at. Curved screens are more expensive and more of a hassle to setup. If you don't have a specific reason to go curved I'd stick with a flat screen to save yourself any headaches down the road.

There is a SLIGHT amount of picture degradation using an AT screen as compared to a good reference screen and it might not be even noticeable depending on your seating distance. However there is a HUGE improvement in sound being able to use identical front speakers with proper placement using the AT screen. Unless your a die hard videophile I'd use the AT screen.

If you are going with in wall speakers yes sound will be better and more uniform having them all the same hight and type. However in walls don't image the best or have the best sound in fact in walls typically have better sound because they can control the cabnet and floor standing have the best because they image the best and disappear into the room. You will learn everything is a compromise.

So floor standing with a matching center is best it also allows you the greatest choice of screens and many more options but you need room. If you are forced into useing AT screens they are not bad but you are limiting your choices and you can't go with the more advanced screens lie the black diamonds and stuff. There is also almost no AT HC 4k screens that are not a weve.

In walls can image fantastic. I'm not fond of the cheap in walls that are open back. But a well made enclosed in wall or a speaker designed to be baffle mounted has many advantages over free standing speakers. The room will have a lot do with imaging as well. The disadvantage to in walls is they are not easy to toe in, unless you design the wall that way:-) Here is an article on baffle mounted speakers by a top acoustic engineer.

http://www.triadspeakers.com/cinemaplus/partners/pdfs/pmi/040601_baffled_again.pdf

Chris Seymour just posted some test results of the Elite 4K material. Even though Chris may not be the most disinterested party, it is probably safe to say that EN4K is a very different beast and it's unlikely that the Elite material would be able to match its performance both in terms of PQ and acoustic properties.

If your seating area is over 10ft away, you may want to look at Seymour Centerstage XD. It is much brighter than their uberexpensive EN4K cloth and Elite's A4K. The gain/brightness advantage maybe especially important for 3D. The Cenetrstage XD material is available for DIY if you want to safe some money.

If you go with a quality AT screen like the En4k, it will not degrade image quality. It does suck light, though. Be prepared to either downsize the image or upsize your projector. I find the calculator at www.eliteprojectorcalculator.com useful and easy to use. Figure on .8 for the En4k gain. Could actually call it .75.