The ASUS P8Z68-V is the best for OC the i7-2600K; SLI and CF support. The GPU depends on your budget, resolution and games you play. The update to the ASUS P8Z68-V (or Pro) is the ASUS P8Z77-V or ASUS P8Z77-V Pro.
The ASUS P8Z77-M is a mATX and no SLI/CF support and is not a great OC'ing MOBO. The Gigabyte GA-Z77-DS3H is a mediocre OC and CF only MOBO.
An alternative is the ASRock Z77 Extreme4.
The Z77 vs Z68 makes little difference with a SB CPU.