Yeah man, that would be brilliant to see when you get a chance. I like this idea of having some sort of planned soundscape and having a few options to choose from and see what works best for me would be great!
You got it brother! :) Ok, this sort of thing isn't for everyone, but it's something I always try to do as I'm reviewing a mix and getting my ducks in a row as I am also getting familiar with the mix. Creating a sound space is important to me. Even if I'm the only one that feels that way, it has helped me loads with controlling mixes.
The illustration I'm going to share with you was a rock mix I did for a client. Of course this stuff changes from mix to mix, but in this particular example, I felt it was the best way to go and we came out with fantastic results. I'll post the illustration and then explain it all.
Better image:
http://dl.dropbox.com/u/4909348/DanziLandMusicSoundStage12.jpg 
What you are seeing here is a basic sound stage using pictures of instruments and how they are panned. If you were sitting in the audience this should be what you are hearing as well. Though most sound systems are mono at clubs, in a real concert situation or in a theater hosting a pro band, you'll more than likely get stereo.
The line running through with the arrows represents our pan field. The imager stuff I will explain more about later in this message.
Drums: Let's start with the drums as they always seem to take the most time and are discussed quite a bit in terms of engineering. I'm one that doesn't like extreme drum pans in my mixes unless the mix calls for it. I see no reason to go further than 50% in panning or the drums become disconnected. What you see is just that. An illustration using Superior as my subject because the client used that exact kit. As you can see, we never go out of the 50 % pan field on the drums, therefore keeping them tight and not all over the place with tom pans and cymbals hitting all over the place. Sometimes I may go out to a 75% pan on the drum kit, other times a 40% pan. It depends on the mix, the genre, the kit being used as well as the other instruments supporting the mix. By the time we add some room to the kick and snare and then process the snare with a bit of verb, they no longer occupy a basic, centered pan field. They too reach out beyond the center to an extent.
A verb on a snare should not be a stereo verb that allows that snare to crack from 100 to 100. The snare is behing the kit. The snare should stay between the floor tom and the hats or go no wider than the hats and the ride cymbal. Sonitus Phase and plugs like it are your friend when controlling the width of effects. Or you use the width controls in the Sonitus plugs or any other plugs that offer that feature. But don't forget to do it because effect panning and eq is as important as instrument panning and eq.
Guitars: The guitars you see are 4 layers. The 2 main guitars that drive the song are panned at 85 L/R. The ones at 60% L/R are supporting layers that come in during chorus parts. The space they take up during that time was essential to this mix having the modern rock impact it needed. You should eq these differently and can also effect these supporting guitars with a bit of chorus just to make them a little thicker. Their volume, however, should be supportive, not as loud as your main guitars.
Bass: The bass is self explanitory of course. :) Though some people like to slightly pan their kick, snare and bass, it's not someting I feel needs to be done for the simple fact of what Shad mentioned about reverb. This is where you can make a bit of a difference eventhough something may be panned center...and this is what my "imager" diagram is all about which I will share with you now. But as far as bass goes, unless I add a slight bass chorus or a layered, hybrid bass sound, this is the only instrument that maintains a solid, centered pan.
Vocals, back ups and imaging: When we place something in a pan field, we can literally stretch it out to be something it really isn't by way if imaging. The imager relies on a stereo effect before it and can only be used AFTER that effect. For example, let's look at the lead vocal. It is centered. However, with a slight doubling effect using the Vocal plug offered in Sonar or a slight chorus or a verb, and we can literally stretch that vocal out to where it can sound like the size of it is going from 50L to 50R. The imager you use will dictate how wide you can notice the differences. We can use a Sonitus Phase plug or a Waves S-1 to handle this. However, a PSP Stereo Enhancement plug will do something completely different to the vocal in question. It depends what you use and what effects you have before it. You can process on the vocal track itself or use a bus if you want.
We could also use a HAAS effect on instruments and then run another instance reversing the HAAS to the other side for some cool effects. There are so many ways you can do this stuff, it's insane really. But once you create the texture, you have to know how to control it or you get a mix full of thick mud that doesn't have any impact.
The same with back up vocals. In the diagram, we are looking at two stacks of vocals that were sent to an instrument bus. One stack was panned 40%L, the other 40%R. Once in the instrument bus, we can process effects on them as an entity and literally make them sound like they are stretching out to the 60% L/R pan field. This also fills up the space in between and we are not walking over top of anything.
Let's revert back to the support guitars that are panned at 60L/R. We have choices here to where we can create a room sim, compress it and then control how that room sim spreads on those guitars. In this example we want those guitars to go from 60 to 85 and stop right where the main guitars are hitting. We want the main guitars to spread from 85 to 100 so we are filling up the space and leaving no gaps. This is how modern sounding stuff fills out the spectrum.
Our back up vocals stop right where those support guitars stop and if we have to slightly pan our effects spread to 55 instead of 60, we can do that if we notice anything walking on top.
Your next question may be "why don't you use any wide pans Danny?" The reason being, I like to keep them for special effects that leap out to a listener. When you hit them with a wide pan, it sticks out because we haven't used it to the extreme anywhere. This is great for vocal effects, special processing effects and anything else that you need to fly in as an impact type of thing. To me, when people hard pan, it can fatigue a listening experience as well as sound too disconnected. It only sounds good in headphones and usually sounds too separated in real monitors or in a car.
There are no rules of course, but these are the things I have followed that allow me to keep everything in check. If you want tight mixes with impact, keep your pans tighter. If you want a disconnected Beatles mix, pan everything to the extreme. I love the Beatles but I was not down with some of their decisions regardless of how famous they are. I can throw up listening to a drum kit that is hard panned for the sake of being hard panned. But that's just me....no one else has to think, act or engineer as I do.
A note about thick/big sounds: The imaging stuff can be useful for lots of things. But make no mistake, nothing touches a sound that is recorded "big". We can simulate, stretch, widen, enhance, it is not the same as purposely recording a big sound. To do that, you need a big sound to begin with, several mics, a good room and the know-how to pull it all together. In most home studios, people don't have this luxury so they are left with imagers and the like. You just have to stay focused and not over-use any of this stuff because you can disconnect the mix, add artifacts and bring on synthetic phasing that just sounds bad. So just be careful...and whatever you do, don't etch ANY decisions using imaging in stone while listening on headphones. I don't care how good they are or who recommended them....don't do it man. It won't be a very nice outcome.
Anyway, I hope some of this helps you Matt as well as others who may be reading my long winded posts. These are some of the things I teach here that keep people coming back for more. I also apply everything I talk about to my own mixes at all times and have made a really good business with this stuff. If it doesn't work for you or anyone else, my sincere apologies. But it has worked for me and I felt it was worth sharing to the extent in which I have. Thanks for reading. :)
-Danny