Alot of people have used the Elite version, but not too many have used the Alpha. There really isnt much difference between the two besides coil and top plate though.
Their pretty good for daily beating, and if you build your box right and feed the subs enough power you could easily compete with them.
I'm grappling over whether or not to buy one for my new system. I keep hearing contradicting things about them. I was looking for an SQ sub, but the recommended enclosure for these is a small ported box. A lot of people swear by them and a lot of people are still hesitant because there are no specs available yet.