Reference or Non Reference GTX 670 for SLI

[Steel_Nugget]

I currently have a 1080p monitor, so SLI isn't needed, but I plan on getting a 1440p monitor. When I get a second GPU should I get a Reference design card? If I got a reference card it would be the EVGA FTW.
I currently have a EVGA GTX 670 FTW 4gb which is a GTX 670 clocked to the speed of a stock GTX 680 with the GTX 680 cooler. My case is a NZXT Tempest 410 Elite http://www.newegg.com/Product/Product.aspx?Item=N82E16811146080
And for a Non Reference GPU it would need to be a GPU factory OCed to at least 1006 on the core clock, or a Asus Top GPU with 4gb of Vram, so what ever you recommend.
Thanks!

 

[TropicoSuarez]

I currently have a 1080p monitor, so SLI isn't needed, but I plan on getting a 1440p monitor. When I get a second GPU should I get a Reference design card? If I got a reference card it would be the EVGA FTW.
I currently have a EVGA GTX 670 FTW 4gb which is a GTX 670 clocked to the speed of a stock GTX 680 with the GTX 680 cooler. My case is a NZXT Tempest 410 Elite http://www.newegg.com/Product/Product.aspx?Item=N82E16811146080
And for a Non Reference GPU it would need to be a GPU factory OCed to at least 1006 on the core clock, or a Asus Top GPU with 4gb of Vram, so what ever you recommend.
Thanks!

The thing is with SLI, you have to have the same GPU, the same RAM, and of course an SLI bridge. It's best to have one of the same exact cards, simply for redundancy and simplicity, as you'll run into less complication when they are exactly the same card. I would by another one of the Graphics cards that you already have.