I have been upgrading my gaming rig two or three weeks ago with Core i5 3570K and Gigabyte 670GTX with 4GB RAM (for large texture pool games like Arma 2), and I had to chose a new board as well.
I bought the GigaByte Z77-D3H, and let me tell you, it was awful-to-horrible. The BIOS was a mess, the whole board system was unstable on stock clock values of the components - RAM errors, blue screens, restarts. It was the 1.0 rev though, 1.1 has larger secondary PSU connector (8 pin instead of 4 pin), so power stability might be an issue, but I have returned the board to the vendor.
I replaced it with Asrock Extreme 4, and it's much better - the BIOS is very nice, the system rock stable, the overclocking options much more logical and consistent.
Having problems with Gigabyte 8800 GT in the past (revision with bad memory, some games did not run at all), I am not that impressed with Gigabyte Hardware. Asus may be a better choice overall.
Just one word of warning I learned the hard way - the new chipsets boot to UEFI by default, and it is probably wise to install the new OS on UEFI an partition, since the good old BIOS is being phased out. There is a nasty bug in Windows 7 64bit that causes the boot sequence to hang if you have a SINGLE hard disk connected that is still MBR (not GPT) containing an extended partition with logical partitions. What I had to do was to install on a clean GPT formatted disk, then backup all my important files, reformat all the old disks from MBR to GPT (the disk must be empty to do so), and move the data back from the storage. I spent two days with this tedious cleanup, so BEWARE!