Sony Xperia Z, was put up for sale in the U.S. priced at $629.99. But unlike the latter model, the Sony Xperia SP is not resistant to water or dust, and the Xperia SP is powered by a dual-core processor instead of the quad-core silicon found on the Xperia Z.
If you're interested in a mid-range Xperia model with a nice sized 4.6 inch screen and a decent battery (2370mAh) with Android 4.1 installed out of the box (which means that Project Butter, Google Now and actionable notifications are all already installed on the phone), click on the sourcelink to pre-order the Sony Xperia SP.
source: SonyStoreU.S. via AndroidAuthority