Is it worth upgrading from 660ti OC 3GB SLI to one 970GTX?

I don't care for power reqirement or heat.

no

No ,

The 660 ti sli are about equal , an "upgrade" would be 970 sli or the likes.

agreed!

2x 970s are the sweet spot right now! If you can find them anywhere! That's what I did!

Well you would probably get better power consumption and thermals with the 970. However FPS wise you'd probably gain very little.

not till one of them dies

They're about equal power so unless you need the new features of the 900 series then no, it's fine.

Short - No

https://www.youtube.com/watch?v=spZJrsssPA0&feature=youtu.be