why do you have a z77, and a locked CPU? (non-K)
anyway, no. The motherboard doesn't bottleneck anything. You could have a PCIe lane 8x, but that one is 16x, so not even there is anything bad.
Since you have a correct socket for that CPU, the adequate PCIe lane for the GPU, 6GB/s sata connections, I don't see where you could possibly be bottlenecked. In fact, that chipset is "too good" for that CPU (like i said before).
Finally, that motherboard is no crappy thing

And no, you wouldn't see any improvements, on changing the motherboard alone.
Are you having issues with your build? Lags, freezes, low frame rate?