Do you have the AC line to support that amp?
That amp that you are looking at is, no doubt, a monster. Emotiva is also a good company that generally stands behind its products. On the other hand, I've also read of some of the problems that others have had with Emotiva products that weren't taken care of to the customers' satisfaction.
In any case, your stated reasons for wanting the XPR are quality and head room. There have been other threads regarding the XPR amps, so I checked out the specs on them. I know that specs don't tell the whole story, but if you read them with the understanding that they are published by the manufacturer to cast a favorable light on the product, you can read between the lines and get a bit of information.
What bugs me about the XPR is that although it is rated at 400 wpc at 8 ohms, it is only rated to 600 watts at 4 ohms. Most really gutsy amps that I've looked at usually come close to doubling their power rating when the impedance is halved. I really don't know how this would affect the performance of an amp the size of the XPR, but it is a consideration nonetheless.
I also looked up the specs on your speakers. If their efficiency is truly at 93db, I've gotta tell you that 400 watts of amp on each channel is going to be a lot of overkill. I'm wondering how much of the range of your volume control you're really going to be able to use.
Really, a good amp rated at 100 wpc at 8 ohms and 200 wpc at 4 ohms will provide more than ample headroom and will get loud enough to just about blow your brains out.
The point that I'm trying to make is that with the XPR you will be paying for the quality of the components, but you are also paying for power that you will likely never use.
If quality is your concern, I will go out on a limb and say that better quality amps can be had for the price. I just saw a 150wpc, 6 channel Classe amp for sale in the ads for under $1400. I'll go further out on a limb and say that the Classe is a "better" amp than the Emotiva.
I do believe that the best deals can be had in the area of amplifiers on the used market. Come to think of it, I don't think I've ever bought a brand new amp.