Speakers for a large vaulted room?

Well I would place the speakers no more then 8 feet apart and sit no more then 8 feet away from them. Remember this is not a PA System.... That should solve most all your problems unless you are married...

The best

PS. I am a dealer. Not for any of the gear that you have however.

My room is larger than yours, and I drive my Tannoy HPD 315's (12" Dual Concentric) mostly with 35Wpc, an old VAC PA 35.35. With these vintage speakers (though with custom cabinets, custom crossovers, and current-version "Hard Edge" surrounds from the Prestige line), the 35 year old drivers aren't quite the antiques they were, but anyway, they pressurize my large room very well, and the bass is outstanding. If you can, try to audition Tannoys, the 15" Glenaire should work nicely for your needs.

Especially since the ceiling limits so much I would continue to do the nearfield listening; it'll eliminate a lot of room issues.

You need to determine if you really want to trade away the panel sound. If you do not realize how vast the soundstage is, you may switch and lament it. I would suggest that if you have the space you might add another speaker to your stable rather than switch. If you still like the maggie, then keep it and swap them around occasionally. Check out my system here; you'll see I keep two speakers available to enjoy. This has brought tremendous pleasure, far more than owning one technology. I think you'd really enjoy having such variety.

I used the Tannoy Glenaire in review and it would make for a lovely nearfield speaker (see the review at Dagogo.com). It is a very easy speaker to drive, so it would be quite compatible with your current amp.

I would not preclude the exchange of amplification. If you like the pre, that's fine, but you've got a serious power problem with the clipping. Upping the power will do wonders not only for avoidance of clipping but in many other ways including extending the soundstage - a wonderful improvement and having more dynamic power to get better control of the speaker's drivers. The difference is quite dramatic. I would suggest no matter what speaker you secure that you eventually upgrade the power of your amplification. The nature of the speaker's sound will improve significantly when you do.

The only other solution to get more out of your amp performance is to move much farther toward a high efficiency speaker, something around the 92-95 dB or even higher range. That would be harder to find in a speaker with a smaller cabinet and will not solve the problem of your panel speakers clipping should you choose to keep them.

In relation to your room/logistics, perhaps you are thinking that you'll get far more placement options by shortening your speakers? Yes, you will. Lowering them will allow you to spread them out more, which will in a sense compensate slightly for the loss of taller soundstage; you can always tilt back the speakers to experiment with raising the soundstage of a shorter speaker. It may or may not be to your liking, but it's an option.

If you go with a shorter speaker and move them outward toward the walls, you will likely want to treat the walls with sound products, i.e. sound panels. In fact, even if you keep the Maggies I'd likely put sound panels on the head wall to diminish unwanted reflections. You might be surprised at the change in the sound of the room. :)

My room is not vaulted but it is 28 foot long and 20 foot wide plus it has a 9' ceiling with a 18" tray on top of that. Plus every corner opens up to a hallway, another room or a stairway upstairs (adding even more volume to fill.

I have had Genesis 501s with built in subs/amp and now I have Legacy Focus powered by a Legacy power amp for the stereo channels. I think it is 250 wpc into 4 ohms.

The legacy speakers are high efficiency and fill the room well. I have the speakers about 8 feet apart and my listning position is about 13' away from them. Sometimes when I am doing serious listning I pull the speakers from the wall which gets them about 11" from me.

I have not ever felt the need to add a sub or more power and the dynamics are great even with rock, classical or anything else I listen to.

Give the focus or whispers a try in the Legacy line up.

I have two listening rooms in upstairs rooms (in my home & cottage), but neither is as large as yours. Never the less, I've never had much luck using panels of any kind in those rooms. I just don't think dipoles lend themselves to angled side walls. I'd try shifting to a good dynamic speaker, not because of peak output, or sensitivity, but because I think you will have a much easier time getting integration with the room. Also, assuming it could be done, I'd consider setting up a near field listening set up turned sideways, with the speakers against one of the sloped walls, and you sitting against the other. This obviously wouldn't work with the tall Maggies, but a pair of short towers, or mini-monitors could be just the ticket set up that way! I wouldn't think in terms of "filling the space" so much as using the space to keep the room from getting in the way of the speaker/ear interface.
Cliff