I don't know of any resources that discuss what speakers work in what room situations. I believe there are some general rules of thumb that have been discussed in a lot of different threads. There are guidelines where a certain speaker design is best suited for a situation such as near field listening requires near field monitors, which I don't believe applies to you because even though your speakers are on the long wall and you sit relatively close it doesn't really appear to be a near field situation. And there are situations where a speaker is designed for being against the front wall which does not apply to you since your speakers will be about 3 feet out. And there are speakers that are designed to be placed in corners, which does not apply to you either. And there are situations where a speaker type has requirements to be placed well out in to the room to give it room to "breathe" so the dipole reflection effect works off the front wall (like Maggies) and this really rules out a speaker type for you rather than rules it in. I think, but I could be wrong on some points, you really should rule out dipoles as well as speakers designed for corner and near front wall placement. That leaves you a lot of options of I guess what could be called traditional speakers. A lot of monitor style speakers, or smaller floorstanders should work.
And since you will be sitting quite close to the rear wall, you probably should treat that wall for the reflection bouncing off it directly to your ears. I'd allocate some of your budget to that. I used to have a setup where my speakers were on the long wall and I sat right on the rear wall and there was a nasty reflection. To me after determining what speaker design type is good for you room and placement, and getting the speaker placement dialed in (distance from the front wall, distance from speaker to speaker, and toe in), room treatment is next and almost as important as the other two. And in your case that rear wall reflection is a make or break consideration because you could address the first two things but still have poor sound because of the rear wall reflection. If you are concerned with the looks of the acoustic product to go on the rear wall, you might consider getting one of the GIK art panels with your graphic of choice printed on the panel. Very affordable products.
http://www.gikacoustics.com/gik_artpanel.html
One resource that I can think for getting great information on what speaker type would work for you, and which may validate some of the theories I mentioned above (keep in mind I'm no professional and my suggestions may be wrong), is talking with an industry person. Especially since there isn't a one-stop online resource of this subject that I know of. One person I can think of that could help you understand this subject is Duke from Audio Kinesis. He is a dealer and a speaker manufacturer. Based on what I have observed in many years of being on audio discussion boards he is the person I would reach out to if I wanted to know more about what speakers work in what types of room setups. Even though you might not buy from him in the end, he has a superb reputation for being helpful.
