It's a little confusing, but BOTH
the Sapphire 5830 cards are the Xtreme
The $109.99 card comes in a box labeled "Xtreme", and easily clocks to 1000 MHz
with the TriXX utility. Me and a friend ordered these, and are loving them (we get up to 330 Mhash/s, stable).http://www.newegg.com/Product/Product.aspx?Item=N82E16814102878
The $129.99 (+ $7.56 shipping) card also comes in a box labeled "Xtreme".http://www.newegg.com/Product/Product.aspx?Item=N82E16814102946
differences I know of is that the $129 card has a full-sized DisplayPort connector, while the $109 card has the Mini-DisplayPort adapter (like a Mac).
Honestly, the $109.99 card seems like the better deal. It is $27 cheaper than the other one, and has a more-common Mini-DisplayPort port. I already have adapters for that since I work with a bunch of Macs.
I haven't seen anything other than the DisplayPort size on the $129 card that makes it any better.