Do I need a Sigma DG 30 mm F/1.4 HSM EX DC Lens for low light with these other lens.

I have a CANON 17 55 F/2.8 AND A TOKINA 11-16 f2.8. Do I really need to keep the SIGMA for low light inside shots? What would you do?

Usually people ask these questions when they already WANT to buy a particular lens Truth is - only you can answer it - depending on what you shoot, your purposes and tastes. If you have the money to spend - f/1.4 sure is helpful in low light. Whether it is more helpful to you than your f/2.8 in your particular circumstances - no one can tell you that.

I have the 30/1.4 and a 17-50/2.8 and I need both but the post above mine is the first thing you should look at.

Firstly do you earn your living, or a SUBSTANTIAL part of it as a photographer? If the answer is no then no you do not NEED any new bit of photographic kit, but if you have the cash for a new toy available then answer the following questions to see what is the right course to follow. If you are a pro the question is do you do enough shooting in low light conditions that it will earn it's money back reasonably quickly, then you still have the following to answer. Now the really big question is would a f/1.4 standard lens help in low light photography, and I have to say yes of course it will it's two whole stops brighter than your zooms although the DoF at those apertures may be a bit thin depending on what you are actually shooting. I would have a look at your existing photos, and this is where applications like Lightroom help as they can quickly show you what FL's you are using, and also what the aperture shutter speeds and ISO values are. If looking at the numbers shows that you are using from around 28 to 32mm on your zooms, and wide open at high ISO's then yes the 30mm f/1.4 would make a good purchase for you, as you are likely to use it. If on the other hand it shows that you are using a different focal length range more often, then look to buying a fast prime closer to that focal length. You'll get much more use out of that, as it will suit your particular shooting style better.

Alan