Are you really sure what you want or need? I'll suggest you to take a look of photos what you have taken in a last year and look what there is you want to improve / what is not right. Is that gear or photographer related? What focal lengths you have used most? Take a look of photos taken with similar or "worse" equipment about similar subjects you photograph. There are lots of web sites to look at where you can find even full size samples (for example
pixel-peeper.com). Ask yourself that are you buying because you need or because you think you need. Now the scale seems to be so wide that you try to cover everything and nothing seems to really fit. What others think doesn't matter in the end. What you like and what you get good results with matters. Ask yourself what there is in my current equipment that I don't like. If you like your lenses don't sell them just to get "better" ones. You may not like them. Best lens is the one you like to use.
That said, I still suggest you to buy Sigma 30/1.4. I regret not buying it some time ago when I saw a good deal because I read some reviews that said it is a bad lens. Then I looked full size samples of similar photos I like to take and it changed my mind. It is more than enough for me. Even corners when stopped down. There are people that say it is a bad lens but in my purposes it is more than enough. I'm after one at the moment. IMO 15mm limited, 30/1.4 sigma and DA 18-135WR would cover quite a lot of ground.
And to answer the question, I would go either 10-20mm/4-5.6 (older screwdrive version; cheap, light and good quality) + 30mm/1.4 + 50-150mm/2.8 or 17-50mm/2.8 / 17-70mm/2.8-4.5 + 50-150mm/2.8 + 150-500mm/5-6.3 depending what I want (the first being "creative photographers setup" and latter being "sport and wildlife photographer setup"). I may be wrong but I got a feeling that you may be buying just for the sake of buying. It may be the road one have to walk (I have
) but in the end I bet you will regret selling that DA 15 limited