There is no reason why you can not go top, all you need to do is overclock the CPU to the max and then get a reasonable run out of two cards.
The thing to watch out for is bottlenecking the GPUs as this puts a lot of stress on the CPU which in turn gives more crashes than the gameplay.
I was at 5.2ghz for my stock run. Gpu usage was decent, but was not 100% solid on both. Think ill need a 6 core to catch you up tbh. At 1440P i think id be closer, but you can't run that can you on 290's. Mind you, you could if you use CRU to create a custom resolution.