Wharfedale Denton 80th Anniversity speaker: Best stand height for them and brand??

I just purchased a used/mint pair of Wharfedale Denton speakers as an alternative to my Golden Ear Technology 7's .  They are what many testimonials claim: an outstanding speaker which does almost every thing right, and is also musical.  The manual  is not very specific about the height of speaker stands, or distance from back and side walls.

In an 12.5X15 ft room, what might be the best height for them??; I have them on a 21.5 inch stand, and they sound very good. However, instinct tells me they should be placed on a 25 or 26 inch stand so as to elevate tweeters to ear level and possibly reduce low end or lower mids thud.  I sit on a low  couch. 

Without a doubt the Dentons are remarkable speakers, though I have detected on certain CD's a tad of tinny sparkle when they go loud. I am sure they are broken in or close to it, but would like to optimize the performance of this unbelievable speaker that is very difficult to turn off, and go to sleep.  Comments, advice, suggestions will be greatly appreciated.

*****BTW, they can be bi-wired. Does it make a difference in sound quality with this particular speaker. .  Thanks, Jim.