Intel® Core™ i5-2500K Processor (6M Cache, up to 3.70 GHz)
http://ark.intel.com/products/52210/Intel-Core-i5-2500K-Processor-(6M-Cache-up-to-3_70-GHz)
Max Memory Size (dependent on memory type) 32 GB
Memory Types DDR3-1066/1333
# of Memory Channels 2
http://www.gigabyte.us/products/product-page.aspx?pid=4144#sp
GA-Z77X-D3H
Support for DDR3 2400(OC)/1600/1333/1066 MHz memory modules
It doesn't refer to FSB only that "Some Intel® Core™ processors require a graphic card, please refer "CPU support List" for more information."
The CPU only supports 2 ram modules so if you intend on 8gb then
2 x 4gb DDR3-1066/1333 (to ensure no errors) in slots 1 & 3
I'd suggest the Crucial brand rather than Corsair, personally, I think those ram sticks with those fancy heat sinks do more harm than good.