Sigma have just confirmed the price of the Sport model at $US1999.00.

The C model seems to be a down specced version with 20 elements in 14 groups as opposed to the S's 24 elements in 16 groups and probably without the trick coatings.

The overview on both models from the Sigma website:

The 'C' version:

The Sigma 150-600mm 5-6.3 DG HSM OS Contemporary was created around the concept of maximum portability meets utmost image quality in a variable aperture hyper-telephoto zoom lens. Light weight and compact, this s zoom can handle any long-reach photographic situation one may encounter. This 150-600mm Contemporary boasts updated Sigma technology such as a quiet and optimized Hyper Sonic Motor (HSM) and a new Optical Stabilizer (OS) with an accelerometer for improved panning photography both vertically and horizontally, essential for birding, wildlife and motor photography. The Sigma 150-600 Contemporary also touts a new zoom lock switch that can be locked at any focal length and a new manual override (MO) switch is incorporated for improved focusing control. Working with the Sigma USB dock, this lens allows for maximum customization such as firmware updates and adjustments to the focus limiter, AF speed and OS view.
The 'S' version:
Designed and executed for the most demanding types of photography, the Sigma 150-600mm 5-6.3 DG HSM OS Sports lens is the new standard for telephoto zooms. Boasting 2 FLD glass elements (performance equal to fluorite) and 3 SLD glass elements, the new Sigma 150-600mm Sport produces incredibly sharp images y through the entire zoom range. Chromatic aberration is controlled at the long end of the focal length through the optimized design of the glass elements and a dust and splash proof construction ensures a high degree of durability. An updated optical stabilizer (OS) features an accelerometer for improved panning photography both horizontally and vertically, essential for birding, wildlife and motorsports photography. The Sigma 150-600 Sports also touts a new zoom lock switch that can be locked at any focal length and a new manual override (MO) switch is incorporated as an option which is activated by rotating the focus ring while using the autofocus. This state-of-the-art lens is equipped with advanced Sigma technology including an optimized, quieter AF, water/oil repellent coating on front and rear elements and Mount Conversion service compatibility. As with all Sport line lenses, the Sigma 150-600 works with the Sigma USB dock for maximum customization allowing for firmware updates and adjustments to the focus limiter, AF speed and OS view.
Both models are listed as being USB Dock compatible although it appears the 'C' version has less functionality.


I'll be most interested to see how the two compare side by side.