The upgrade would be for gaming purposes of course. I just want something of nicer quality and I do not like my current monitors for dual setup. Also gaming and multitasking didn't live up to the hype for me. Most games run like crap in fullscreen windowed mode, or don't support it; defeating the purpose if it doesn't. You'll be alt+tab or minimizing out anyways. Only MMO's have worked out for fullscreen windowed. In shooters you'll lose your mouse. And the old Saying that I get to monitor (what?) Facebook? While gaming Isn't really worthy enough of a defense.
So in the end, the other monitor is just a paperweight when gaming.
Of course it's BEAST for multitasking when doing schoolwork, work or web-browsing etc. That's all I'll miss.
If I was you I would do it only because I don't like having a dual monitor setup because of limited space on my table and more wires to deal with it.
This could also be a plus if upgrading. Space is certainly a problem.