Lens suggestion - prime, or?

Thanks very much Reilly.  I'm not quite giving up on that 18-70 yet, as was pointed out I certainly do need to try it without the filter.   But I'll check out that Sigma also in case I do decide to go ahead and replace it.

I haven't looked into the 40Micro before, I will go do that now.  Hopefully, the 18-70 ends up being ok, as it somewhat ideal in covering the range for me (since then I have the 70-300).  But I really would like a faster lens.