Originally Posted by ClambakeSkate
I have the Sigma 30, and it is just as sharp as they say it is. I have heard good things about the 19, as well, but I never made the jump as I have the 16. The 16mm is definitely not worth the money, mine came with the NEX-3 along with the 18-55.
Sell the 16-50, get the Sigma 19, and pick up a 50 of some sort. I have a Pentax PK-mount 50 f/2 that I have used for a good while, and I just picked up a Canon FD-mount 50 f/1.4, The Pentax was ~$35 (~$45 with the adapter) and the Canon was ~$60 (~$70 with the adapter). Your kit may be less flexible, but in the end I think that you will become a better photographer. Manual focus is super-easy with focus peaking on the NEX models, and the wider maximum aperture will give you more control over your images. Also, you should come out ahead after selling the 16-50.