As much as I'd love the kop to be extended and significantly improved, I agree that in the short term the SS would be the most viable option. If we put a 5k second tier, with lots of corporate hospitality etc, I'm sure that we would achieve the ROI. Of course that all depends on staying in the prem, but let's face it, we are a team pushing for top 6. Let's think positive!
Just imagine the pigs

I'm creaming myself at the thought of how they would react - some of them would literally not be able to take it! Also a SS extension would give us room for growth with potential new fans and a place to put kop season ticket holders when/if we decide to completely re-do the kop.