I have seen somebody post a result with a lightning 780Ti already and I seem to remember them hitting a wall at 1700MHz and not being able to go any further, so that is something else to consider when looking at what graphics card you want to buy. Have you considered getting some older card like the 8800 series, volt modding them and getting some results with them? They do have a much higher cold bug than your 780Ti and I'm sure they'd run a lot cooler so at least you might use up a lot less LN2 which is also cheaper in the long run. Another card which I have only ever benched on DICE is the 4870. That's worth quite a lot of points too so it will help with your league ranking as well
That might help you to learn a little bit more about different drivers, tweaking volt modding etc so I suppose that will help you to get better results in the long run?