Just a quick question, I think...
 
I'm considering an upgrade of my 1920x1080 monitor in the next few months to 2560x1440.  The GTX580 1.5GB, I'm waiting for the die shrink on, which will happen eventually.  Maybe late this year.
 
From the specs I've found online, 2560x1440 isn't a problem on the DVI or HDMI connector.  The question is that the maximum refresh rate is 240Hz, but will the GTX 580 1.5GB drive a monitor at this higher resolution higher than 60 Hz (120 or 144) or is 60 it?
 
The question is really "can" it send the video at 120 or 144; not will it actually make that in every game.  That will depend on the game, Team Fortress 2 (easy graphics) maybe, Battlefield 4, probably not.
 
I'm not considering 4K at this time, I've seen it on a 55"+ TV and that does look amazing.  But on this PC, 27-28" will be my maximum size.
 
Thanks!

I'd say get one and try to find a used 580 to hold you to the die shrink or whenever you want to upgrade...

1080p is exactly 56.25% of 1440p in terms of pixel area resolution, so the most you can expect to lose is having your rates cut in half.  But it is game dependent with no one-size-fits-all.
 
FYI, 2560x1600 resolution has been around for 9 years, so don't doubt whether your card can run 1440p which is only slightly lower; the issue (again) is your game choice and its resource requirements by the settings you choose.  
 
That is why I tell people that resolution doesn't dictate graphics requirements, even 4K resolutions have been around for almost 14 years, which budget smartphones have graphics more than the high-end solutions back then than ran those displays.  It is just that games have gotten more resource intensive over the years, and that is the only reason for needing such high graphic power and a large VRAM buffer.