Short answer: no
Long Answer: if you do things that require/benefit from more than 4 cores, then Ivy-E will be a worthwile upgrade. The problem is that LGA 2011 is an ageing platform so you'd be buying into less-than-state-of-the-art tech on the chipset side of the world
I agree to that point in principle. Nevertheless, I'm choosing to build an IB-E system this year. I don't even really need six cores -- let alone eight.
I usually take Maximum PC Magazine with a grain of salt. Their reviews seem a bit rigged, only for their selection of what items to include in comparison reviews. But their December 2013 issue had a nice spot on the IB-E
We've also seen here that some Haswell cores, overclocked to maybe 4.4, have some slight benchmark edges to either Sandy or Ivy.
Don't know what to say about the 2600K. I love my SB-K system (@4.7 Ghz). It matches the I7-4770K (@4.4) in some benchmarks.
If the money could better be spent elsewhere (car repairs, medical bills, food, clothing . . . ), your 2600K should still serve. If you have an itch you can't scratch -- as I do -- well . . . Best leave you to that decision on your own.