OK - I think I'm starting to get a better mental image of your room
First up - is there ANY way that you can pull your couch away from the back wall? I'm talking even just 1 foot. The reason I bring it up is because it is very very common to see the couch pushed right up against that back wall and to be blunt, that decreases the sound quality from the front soundstage tremendously. I've helped several friends set up their surround sound systems. In two cases that I clearly recall, we pulled the couch away from the back wall just about 1.5 feet. The wife of one fellow and the girlfriend of the other didn't even notice until I pointed it out to them. If you ask beforehand, they will usually say that they do not want you to move the couch. But if you just go ahead and do it, as with these two friends, they didn't even notice!
Having that gap between your head and the back wall makes a bigger difference than most people would ever expect. Human hearing is amazing. Our brain is able to ignore a HUGE number of distracting sounds if given just enough delay to do so. A 3 foot gap or greater is ideal, but even just the 1-2 foot gap is enough for your brain to be able to distinguish the direct sound coming from your speakers vs. the reflected sound off of the wall behind you. If your brain receives enough delay that it is able to tell the direct sound from the reflected sound, it is able to learn how to ignore the reflected sound to a large degree. Bottom line - dialogue becomes dramatically more intelligible and that is something that everyone can immediately notice and enjoy!
So that's an aside - but an important one!
Getting back to your original question about surround speakers:
Personally, I would not go for the spot above your door under any circumstances. From the way you have described the room, any speaker placed there would be very close to the ceiling and also quite close to the back wall. It's just an acoustical nightmare position and even a diffuse speaker wouldn't be much help because the direct and reflected sound would essentially combine into one, muddy-sounding mess
If mounting diffuse speakers on the back wall is a no-go, then you are left with Plan 'C' - monopole speakers on tall stands right next to the back wall and aimed directly at one another. With your couch pulled out even just 1-2 feet from the back wall, the monopole speakers can then be
just behind you. With them up above you and firing directly at one another, you get sound reflected off of the back wall, off of the ceiling and NOT pointed directly at your ears, which results in the desired "enveloping" effect.
You'll be able to "pin-point" the sound from the surround speakers a little more than is ideal. You'll also get a more noticable (and possibly distracting result) when you sit far to one side and are thus much closer to one surround speaker than the other, but such is the compromise necessary in your situation
The stands I like best are
these Sanus HF1
They are also made in silver if that would look better. Those stands allow you to get the surround speakers up to their ideal height and they come with a very wide variety of mounting options.
Polk makes many, small monopole speakers that would work well for this situation, so that shouldn't be a problem