1) GTX770:
I have a GTX680 which is basically the same thing (ASUS model. Love it.) I play every game at 60FPS. For games like Crysis 3, Far Cry 3, Metro 2033/LL I had to spend a bit of time finding the optimal settings though.
I also force Adaptive VSYNC on for many games. For example, in Crysis 3 I tweak the quality settings so I drop below 60FPS roughly 10% of the time. When that happens I get a small amount of screen tearing (VSYNC automatically turned off with Adaptive VSync). If screen tearing starts getting too frequent I drop a few quality settings to stay synched at 60FPS more often.
2) Wi-Fi:
The Z87 Sabertooth does not support PCI, only the new PCIe. As said, a regular Ethernet cable is "best" however wireless has improved so much it might not make much difference.
Cheaper card of good quality:
http://pcpartpicker.com/part/tp-link-wireless-network-card-tlwn881nd
"Better" card but you may not need it:
http://pcpartpicker.com/part/rosewill-wireless-network-card-n900pce
Other:
They did a lot of testing and discovered the PING speed was generally the most important for on-line gaming and that most wireless products were roughly the same. Not sure if that's correct, but it's what I read. The article concluded that things like "KillerNIC" were a waste of money.
Sensitivity (i.e. theoretical Mbps) is more important to ensure high enough bandwidth for streaming local video. I use a cheap USB stick with a half decent Netgear router and have no issues (I can send almost 7MBytes/sec, my Netflix is about 1/10th of that, and even my BluRay rips are only about 2MB/second).