This Acer is brighter than any of the projectors shownin these room shots below.
Let's take a break and consider the affects of room surfaces, and how that affects your decisions.
My presumption is, you care about good movie performance, and having good blacks, since you are considering, or own this projector. Rooms with a fair amount of light are often just fine for almost all HDTV and definitely sports. They won't be significantly impacted by reflected light from the original image.
That's pretty impressive, is it not? with the Medium rust walls, a bit darker ceiling (everyone still thought it was white - as it was the lightest surface in the room), the shades opened a bit, yet thanks to the darker surfaces, the image is far better looking than the first image above.
I loved having that Stewart Firehawk G3 (in the images above) in my last home for handling a light surfaced room. It was 128" diagonal in a room with a cathedral celing. When I started out there, all the walls were off white, as was ceiling, and carpet was gold. Lots of windows, which I covered with pleated shades - but with no channels. The Firehawk allowed me to have a good picture even with a moderate amount of light (can reada newspaper bright)
A good HC gray screen rejects most of the side lighting. This allowed me to even have my slide window shades open a few inches on sunny days, and still have a large, great football image. If your ambient is coming from straight back near the projector, like rear windows, the HC gray won't help you.
Ultimately, though, an HC gray, or some new high gain high contrast screens. These are going to be the best choice for most folks with lighter rooms, and especially if the lights are on the sides. Consider the especially the Firehawk G3, and the various Screen Innovations Black Diamond screens (different gains, etc.) which are especially good, but also relatively pricey (more than this Acer projector).. Also: Elite's HC Gray, Da-lite's HC-Da-Mat, and so on. Typically we're talking screens with gains of 0.8 to 1.1 gain, some a bit higher. This Acer is inherently pretty bright on all but the largest screens even in 3D, so trading a little brightness for some ambient light rejection is a plus. (Note HC screens are a touch darker in the corners/sides.)
Don't get me wrong, you can go with a standard white surface, but in a light surfaced room, you'll also appreciate the gray surface's ability to lower the overall black levels, in addition to helping "reject" much of the ambient light that isn't coming from where the projector is (straight back).
One alternative to the HC gray, might be a "high power" screen, one with lots of gain - such as 2.0 or higher. Like the HC gray screen there are tradeoffs. I find the roll off from the very high gain screens to be much worse than the less than perfect edge to edge brightness of an HC gray screen. I avoid hi-power screens, but I know some very serious projector owners who swear by them, for the right situation
Bottom line: The projector has the brightness. Now find the right surface screen to deal with the room. All that brightness gives you a good deal of leeway, or to tackle a room a bit worse than the competition can.