Distance from the speakers to the seating position

also depends on the speaker- i.e. most of Coincidents' models use a twin midrange setup, or D'Appolito arrangement. You need at least 8 feet from the speakers for proper driver integration...

Give this a try; you might find something that works better depending on your room, but this is definitely worth experiencing; if you are lucky and you have a good room, this will cause your sound image to focus with clarity you might not otherwise hear.

http://www.cardas.com/search/searchlist.php?area=Insights&content_id=29&pagestring=Room+Setup+4

(you may have to copy the web site address and paste it into your browser; make sure you get the full address)

The manual for my signature 805's says the best location is like Beavis said, at the apex of an equilateral triangle. I always thought I should be farther back. I tried it then and found that it did sound best for me right at the apex.

Depends on speaker.. some larger speakers must be heard far enough away for drivers to blend properly. I have to sit perhaps 15 feet away from my JBL L-200's.
With my Chario Academy 1's I can sit only 6' away and the sound seems to be best even this close. The closer you are to the speaker the less of the "room" you will hear and more of the direct sound of the speaker. I would imagine with something like Klipch Horns you must sit a good 15' away since they use the room itself as loading.

Here are a few links for your perusal:

Immediasound Speaker Set-up and Placement. Immediasound is the distributor for Audio Physics.
Audioasylum Article
Setting-up Loudspeakers by Audio Physics
For surround-setup go to the site below. Click on SACD. Look for the link called "Surround Sound Diagram". This diagram was designed by Emil Berliner Studios, the company responsible for mastering all the DG recordings.
Deutsche Grammophon.
Good luck.