It seams that the two cards in the link below (both sporting nvidias 780ti gpu engine) are identical in every aspect except Gigabyte's version is clocked slightly faster. However the card is almost $50 cheaper? Is there a reason for this that im not aware of? Are other company's (msi, asus, gigabyte) version of nvidias gpu's SLI-capabale?
http://www.newegg.com/Product/Productcompare.aspx?Submit=ENE&N=-1&IsNodeId=1&Description=gtx%20780%20ti&bop=And&CompareItemList=-1%7C14-487-003%5E14-487-003-TS%2C14-125-489%5E14-125-489-TS&percm=14-487-003%3A%24%24%24%24%24%24%24%3B14-487-001%3A%24%24%24%24%24%24%24%3B14-125-489%3A%24%24%24%24%24%24%24%3B14-121-838%3A%24%24%24%24%24%24%24
http://www.newegg.com/Product/Productcompare.aspx?Submit=ENE&N=-1&IsNodeId=1&Description=gtx%20780%20ti&bop=And&CompareItemList=-1%7C14-487-003%5E14-487-003-TS%2C14-125-489%5E14-125-489-TS&percm=14-487-003%3A%24%24%24%24%24%24%24%3B14-487-001%3A%24%24%24%24%24%24%24%3B14-125-489%3A%24%24%24%24%24%24%24%3B14-121-838%3A%24%24%24%24%24%24%24