The problem you had with the BIOS screen is strange, since nothing is being read from a drive for the BIOS to be displayed. You should be able to get into the BIOS without any drives attached. The BIOS does read drives to the extent they are listed and tested to a degree. The corrupted BIOS display seems to be a clue that something is not right, indirectly related to the 520, such as a power connection.
Have you cleared the CMOS/BIOS at any time when connecting your new drives? Was the 520 formatted when you copied your OS to it?
It's premature to decide IMO, that a 520 is not useable as a boot drive on your specific mother board. I've used and currently use 520's as boot drives on several different boards, but not on a Gigabyte board. If that was a general issue with Gigabyte boards, it would be well known by now.
Was your 520 connected to the same SATA port as your Kingston drives? Your board has a Marvell 9128 SATA III interface, which generally do not work as well as the Intel SATA interface. Where were your SSD connected during the OS cloning process?
What OS are you using? What software did you use to copy your OS?