I am looking into a 1.4x Teleconverter for my Sigma AF 300mm F/4.0 APO lens (Minolta/Sony). I have googled around for reviews and comparisons between all the different manufacturers, and I have not figured it out. Tamron, Sigma, Kenko, Sony/Minolta ... which one ? For those of you that have a 1.4x Teleconverter ... What model do you have and what do you think of the image quality? ... so far I am leaning towards the Kenko Pro 300 DG.