I have just posted my review of the one and only available filter system for the great Sigma 8-16mm HSM lens and I like the Lucroit/HITECH system a lot!
Read all about it here:http://www.stockholmviews.com/sigma_8-16/sigma-8-16mm-filters.html

Nikon D7000, Sigma 8-16mm HSM, Lucroit/HITECH filter system