I'm surprised at the number of few alternatives to the 10x Dominator that are out there. There's Surefire's own M6, but it's not rechargeable.
Other than going with a HID light, or specifically a Borealis model, there's not much out there that can compete with a 10x.
Here's 2 possible alternatives though....
A Pelican 3850.
http://pelican.com/lights_detail.php?recordID=3850N
(A Lead Acid version is available also).
It's more of a lantern, and I'm not sure about pricing. 600 lumens, but Pelican doesn't measure it's lumens numbers from out the front. So it'll actually be less than that.
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An Elektrolumens QuadStar Phazer.
http://elektrolumens.com/
(Just scroll down the page a bit).
Looks to be about the size of a 10x, but a bit thicker. 720 lumens, but again; not sure about pricing.
I checked, and these were the only models that haven't already been mentioned as possible alternatives to a 10x. (Well, the only ones I could find).
Honestly, if you don't need a light that immediately turns on, the instant you hit the switch; I think your best bet in terms of price and performance is a Borealis model. Hope this helped.