That's bigger than some mixing studios I've been in...

First of all, what's the furniture layout going to be? Will you be at a desk by the wall, or will you put speakers at one side and a couch on the other? TV in the middle? Speakers against the wall, or out from it?

You'll definitely want some acoustic panels and bass traps for the room.

My first thought is your room dimensions. It's nearly square. Could cause you some standing wave issues in the bass area. Will make some bass notes stand out more than others. There are several people here that can help you with this.  You may want to experiment with speakers at a diagonal to your listening position. I tried this in a room of similar dimensions and it seem to work fairly well. Good luck. Getting it to sound just the way you want may take some time and lots of experimentation. I have found that an accurrate laser "tape measure" is a real time saver when doing speaker placement measurements. 

Any of you sound folks out there have a good book to recommend?

I heard them in a demo room at a dealer. I liked them as they had a 10'' woofer to help with the bass. Only thing is they are electrostats, so they are dipole speakers. Can be tricky to get placement correct. I had a pair of Quads and it took a lot of work to get them right.  They will produce sound waves from both the back and front of the speaker. The back wave will reflect off the back wall and if it arrives out of phase with the front wave will produce all sorts of problems. ML suggests at least a placement of 2 to 3 feet away from the back wall and 1 to 2 feet from the side walls.  That puts you close at your listening position. Less if you place them diagonally. And you would have to have your listening chair right next to the back wall more than likely. I'm thinking with wood floors you have a very reflective room so you are going to have to deal with that for sure. Sometimes an area rug helps. So would adsorbing materials on the side walls at the first reflecting points, and possibly some diffusion as well. Yeah and bass traps as well.  Best to do a lot of research before you start buying stuff. I learned the hard way.  You might consider smaller monitors in a room that size as well.

I did some reseach and bought several books on room modes and speaker/room interactions. Unfortunately they don't always agree on what to do. Take your time is my best advise.

Has anyone used some of the online services that offer advise for a fee?

If you have that much budget you might be happier getting something more exclusive like something from vapor or Selah.  Or the ascend sierra 2 with raal

Soooooooooooo I'm thinking of turning an empty room in my house into a dedicated listening room. The problem is that it's a very small square room with wood floors. We're talking something like 10'x9'x8' here. Unfortunately, this room is my only real option in my house for a listening room.

My current headphone is the HD800. I'd want to get as close to those in perfomance as possible, especially in regards to resolution and detail retrieval.

My budget for the speakers, amps, and related accessories would probably be in the $5,000 range. I've done some googling, but I'm still not sure what I should be looking at.

KEF LS50s, rugs on the walls and a couple of good subs.

Panels or foam would of course work better. In your case the room reflections are your worst enemy, so look for room treatments and constant directivity (as if there was such a thing...).