Most RAM manufacturers won't state that their memory will be compatible with all boards, but at the end of the day it's still just RAM. By using that rule, if your board takes DDR3, then any DDR3 from any company, will work. As long as it's around the same speed (anything faster will run its clocks lower to work), and the same pin count (200-pin, 240-pin, etc).
You can buy any of the G.Skill kits, as long as it's the same DDR type as your motherboard. Your Gigabyte EP45T-UD3LR takes DDR3 memory, so you'll be fine. Get any of their dual-channel DDR3 kits and away you go!