Finally making the jump from 2-way to 3-way SLI. I currently have two cards in slots 2 and 4. Which slot should I put the 3rd card? Also, I have 1 PCI-e power connector connected to the board itself. Do I need to connect another for the third card?
Thanks for all of your input in advance :)
 

I got chance to make 3way SLI too with EVGA GTX580.
Some guy offer me for 230e two used EVGA GTX580 and mine that would be 3 way SLI but it's to risky for me to buy used cards and I wait 780 series.
Mine was new and fabric sealed and because of that I buy.
I mean that would be lot of power for only little more performance than 780 and one card and second for physix is better optimization than 3 cards for gaming. 

First of all, thank you goes out to those who gave feedback on the optimal configuration for 3-way SLI. I wanted to go the route peacock9213 suggested but unfortunately, I had to use slots 1 3 & 6 as the cooling solution on the MSI Twin Frozr III cards I have require more space between them than the reference cooler design. With that being said, I know I might be suffering a very small performance hit but I think I will survive.  
 
In order to accomplish the 1 3 & 6 slot configuration, it was a HUGE challenge to find an SLI bridge that would do the trick. If you are lucky enough to find a 140mm SLI flex bridge, you can use it to connect the cards in slots 1 and 6 and use two smaller flex bridges to make the other connections.

This method works fine but doesn't have the greatest appearance.
 
The bridge I was REALLY lucky to find was the ASRock 3-way SLI-2S2S bridge:

 
It has the appropriate length to reach all the cards and a clean look.
 
 
So far, I have had no issues with the configuration and everything runs smooth.
 
Just wanted to share this as I know there have been folks who ran into this problem before me and hope it might help anyone who is facing this issue in the future.

bcavnaugh
You only need one of the PCIe 6 pin plugged in.

Thanks for the info. I have  the 6-pin plugged into the bottom connector on the motherboard.

MhzManiac
If you already have the SLI connector, you will see the spacing will only allow you to use certain slots. All video cards need their own power or there might be a problem powering up the system. It may power up even without external power to the card, but once you game it may crash.

This thread is from October, 2013.