what speakers to purchase

Be careful of speakers with large woofers that proclaim to go low in the bass. With hardwood floors they will probably couple with it to ruin the sound. British speakers might be good.

In a near perfect cube and with plenty of reflective surfaces I'd be inclined to go for stand mount two ways and a sub (or two) - this may give you the most flexibility for positioning (such as speakers backed up against glass wall but not destroying the view) and oh, BTW - you really must get a rug. I'd suggest ATC 20's and one or two JL F113's because the little ATC's are small yet so powerful that they could fill that space, however, I fear you would find them too forward and too bright in such a reflective environment. You would probably be best served by two way B&W's which tend to have a scooped midrange (get the ones with the crossover to the tweeter way up around 4 Khz so that the natural beaming from the large midrange/woofer reduces the "harshness" in the mids).

I had a nearly square room with wood floors and it was a bass nightmare. And although your cathedral ceilings will no doubt help, if you're contemplating large floorstanders I'd audition before buying. I agree with the post above that stand mounted monitors coupled with a couple good subs might be the best way to go to avoid nasty room effects or the need for lots of additional room treatments. Either way, try before you buy is probably a necessity in your case. Best of luck.

I second the big B&W's, only because a buddy has them in a similar room and they sound fantastic. He had some amp issues, and finally got them really rockin' with McIntosh 501's (which he got because they didn't sound good with my Maggies) and the sound is very full and coherent. Great high's and mids and very tight bass.

Look at Albert Porters system, the room looks similar to how you describe yours.

Thank you for your responses. I took your advice and went with with Wilson Duettes with stands.Matched them up with a JL AUDIO F 113 sub and Cardas clear cables. WOW I was so impressed with how this system performs with the conditions that where thrown at it.
Now I need to find a music server that gives me not only the best performance but the easiest to use...