Can you double check the motherboard. Asus don't appear to make a MSN-E SLi board (i searched) but they do make the M2N-E SLI which is an AMD AM2 Nvidia board.
It actually uses the nforce 570 sli chipset, Nvidia don't do a 500 Sli, closest would be 520.
The 570 Sli link is below...
http://www.nvidia.com/object/nforce_nf5_win2k_9.16.html
Intel Core i7-4790K 4.00GHz - 32GB Kingston HyperX - Gigabyte Z97X-Gaming 7 - EVGA GTX 980 TI SC 6GB - Asus ROG Swift PG278Q