No bottlenecks there, either way, really. The 560 Ti, would have a chance at bottlenecking at super high resolutions though, but so would its AMD equivalent. It's just not a super powerful card, but strong enough for most situations.
A 2600K is sufficient for 2 x GTX 690s or 4 x GTX 680s if overclocked so as said above the bottleneck will be with the GPU not being as powerful as the CPU can handle. No big deal though. All of us without $1000+ worth of gaphics cards and high end CPUs see the same thing. It just means you can keep adding graphics cards as long as you want.