I can usually sex beardies at about 8 inches in length so these guys are easily sexable at that size. Once in a great while a male will fool you because his hemipenes drop on the late side but most times sexing at that size is fairly reliable.
Whether or not they are 2 males, 2 females or a mixed pair the behavior you are describing sounds like a territorial dispute and those can turn ugly very fast, it's probably best to separate them. See my post about "something in the air" for two horrible examples of territorial aggression. Both cases were females fighting each other. While not as common as males fighting, the outcome can be just as nasty.
http://www.ssnakess.com/forums/showt...threadid=19699
Ditch the hot rock! They are infamous for burning reptiles, plus beardies are heliotherms who absorb their heat from above through bony armor plating on their backs. It is infrared and ultraviolet energy they need for proper thermoregulation, not just the radiant heat a hot rock provides.