At the time (right after the whole Sandy Bridge fiasco) there weren't many B3 ready boards to choose from, but I went with an MSI and it has been awesome: http://www.newegg.com/Product/Product.aspx?Item=N82E16813130574 . If you don't think you'll care about SLI then this board looking promising: http://www.newegg.com/Product/Product.aspx?Item=N82E16813130576 . For cooling it depends on what you plan to do with your CPU. Do you plan on OCing it (which would be the only reason to get the 2500K instead of the 2500) a little bit or do you want to push it (4.6GHz or higher?) Corsair has a great new Liquid CPU cooler Hydro Series H100 that I'd eventually like to try.
Just built myself a new gaming rig a few months ago and used the i5 2500k and it was worth every penny. I have a nice little oc of 4.2GHz being cooled by a Corsair H80 Liquid CPU Cooler and my temps are around the 45-50 ° Celsius at full load under Prime95.
http://www.newegg.com/Product/Product.aspx?Item=N82E16835181017
http://www.tweaktown.com/reviews/4257/corsair_hydro_series_h100_extreme_performance_liquid_cpu_cooler_review/index1.html
Check out my Youtube channel: RetroGameClips
Check out my Youtube channel: RetroGameClips