You get free extrass ($78 value) with the amron 17-28mm FE preorder at FocusCamera.
Tamron 17-28mm f/2.8 FE preorders:
In the USA at BHphoto, Amazon, FocusCamera, BuyDig and Adorama.
In Europe it’s available at Calumet DE, WexUK, Park UK and CameraTools NL.
One more thing:
Krolop-gerst added some RAW samples you can download.