Your CPU is not that relevant here... what is your Motherboard ? Do you have a PCIE gen3X ? Card will always work... maybe the limit in your system is elsewhere... maybe not at its full potential ?
It's going to work, but it's not going to be able to fully stretch its legs at lower resolutions. That, and your relatively slow 8GB memory might also become a limit. But it really isn't such a big deal.
I think what your friends are trying to tell you is you are thinking of spending more on one component, the videocard, than your entire computer is worth. That's a big imbalance.
For a system with an i5 Ivy Bridge I'd say an Nvidia 1060/AMD 580 is the most you'd want to pair it with. This assumes we are talking 1080p 60hz gaming here.
I think what your friends are trying to tell you is you are thinking of spending more on one component, the videocard, than your entire computer is worth. That's a big imbalance.
*IF* that's what they're saying, it's still wrong. Hell, a friend of mine put together a new system a couple of years ago, and of the $1500 it cost, half of it was the GTX 1080 (which had just come out at the time). He already had the 2560x1440 monitor (144Hz refresh I think)
It also neglects the fact that the video card is portable over to a newer system.
Whether this interpretation is true, or not, I can't really see why/how OP's friends made their determination that it's not going to work.