I'm going nuts trying to decided which mobo to buy. I want to a get Z77. I'm in favour of the i5-2500k cpu. I'll have either a 6850 or 7850 vid card. I will be using ATX form factor.
What's the difference between all of the different models in motherboards ranging from the bottom of the pile to the very best? What is the cheapest z77 that is reliable, I can overclock and is reasonably future proof, has SLI/X-Fire (I see bad reviews for ASRock so I'm not going there). And if I get an i5-2500k, can I support 1600 Mhz ram?
This will help you compare the i5-2500k ($220 at Newegg in the USA) with the i7-3770K ($350). If you can afford the price difference, it may be worth it. It depends on what you intend to do with the computer.
As for the motherboards... First decide if there are any features you absolutely need, e.g. wireless support, dual LAN, lots of SATA ports, support for three video cards, etc. That should help you narrow it down. Then find some sites that help you compare features.
For example on Asus' site, start here: http://www.asus.com/Motherboards/Intel_Socket_1155/Inte...
Open each MB you want to see in its own tab and click "Add to compare list". When done, click Compare Now. Unfortunately the site is badly designed and I can't send you a URL that goes directly there with some boards already selected. Personally I think I'll get the P8Z77-V DELUXE, but you may find some other model you like more. It depends on the features you need.
On Newegg's site, you can also search for Z77 motherboard, select some results and compare them. For example this page compares two Gigabyte boards: