This thread is actually quite interesting. My turn to contribute...
Lets start off by putting all pricing aside. Imagine we lived in a utopian economy where everything is of no price (economically impossible as it may be [uh oh, I'm ranting again])
All 3 drivers are awesome drivers, all 4 of which I have owned within the past year. I can honestly say that I tortured the hell out of all 4 drivers, all being 12. Each and every one of them took an excess of 2500 watts for burps with ease.
The Brahma and the XXX are very similar in performance. As it has been said, if you like SPL, the XXX has the edge, SQ wise, the Brahma is a bit more potent. How does the e12a fit into this equation? In my honest opinion (using my ears, not paper) the e12a, when in the right enclosure sounds better and gets louder than any of the listed above, the XXX being its closest competitor.
Stephen, no offense intended by this remark, but it seems that you have an obvious bias towards Adire Audio. Of every post of yours that I have viewed, 95% of them are about or pertaining to Adire and the Brahma. Honestly, I can't see how you are able to make any educated remarks about the E12A unless you have heard with your ears what this driver is capable of. You want to look at specs, thats fine and dandy, but there is no tool that can measure the performance of a driver better than the one God himself created; the human ear. Just keep that in mind.