Upgrading from Gtx 760 ti sli to Gtx 980sli

[Firstclaims]

I'm thinking of going 4k but not sure if it's worth it at the moment and if I would be able to play games like gta5 in 4k ultra settings at 60fps.
I have 2 Gtx 760 ti oem 2gb in sli and want 2 Gtx 980 4gb sli. With a 4k monitor(not sure which one yet) What do you guys think ? Oh and I have a 850w power supply.
My processor is I think a i7 4820k 4.2ghz.
Thanks in advance

 

[disturbed force]

At 4k cf 290x does about as good as 980 sli for around half the cash. With that said both setups will not give you a consistent 60fps in gta v with ultra settings, you wilk have to turn down some settings to archive that. Your PSU should run either setup depending on the guality.