Yeah nvidia only will go 3x1, no other variations (I think they are working on 2x1 support in new drivers)
If you are set on nvidia using a 5x1 setup then as mentioned above get 2 cards (Which support a minimum 5 monitors altogether, 1 card runs 3, the other 2, or more..) and use softTH (I love selling this program, its the best freeware out there!!!) At least u can optimise softTH to use CUDA cores (In the config file, nonlocal transport = CUDA32 or something like that) but is limited to dx9.
If you want everything to work sweet and easy then ATI is the go but as was stated you MUST GET THE 6 MONITOR EDITION as when you xfire the video outputs on the second card are disabled (I found out the hard way and used softTH after getting 2x 7970 ref cards). Also if you have multiple mini dp outputs the make sure you have enough ACTIVE MINI DP TO DVI CONVERTERS (As you will be using at least 1 DVI output on the card) ONLY 2 PASSIVE DP TO DVI CONVERTERS CAN BE USED.
If you have enough space between your 16x pci-e slots (3 free slots would be best for this card) then this is the go:
https://www.asus.com/Graphics_Cards/HD7970DC2T3GD5/There are other brands just make sure it has 6 outputs on the card.... (PS: I have seen cards with 5 outputs but only support 4 screens such as my powercolor 6990 and sapphire vapor-x 6gb 7970)