Ok. So I'm going to give my opinion on the matter at hand, then I'm going to respond directly to your previous comment about that curved monitor.
Your CPU is old and underpowered.
For 4K, you're not getting anywhere.
For ultrawide 2K, you going to have almost the same kind of hard time.
Not to mention that it pretty much becomes an issue for your VRAM too since you only have 3.5GB of usable VRAM before everything get's slowed down to a crawl once you dip into that last remaining 0.5GB.
So honestly, 4K and ultrawide are out of the picture for you right now.
However, if you are dead set on having something like that monitor and just playing at a 1080p ultrawide resolution until you get the necessary upgrades to support you playing at UW2K, then you can get all the specs of that monitor but for less at the following link.
Acer Predator Z35 - $749.99
https://www.bhphotovideo.com/c/product/1352852-REG/acer_um_cz1aa_p01_predator_z35_35_uwqhd.html
If it was me though, I find all the ultrawide and curved action to be a gimmick that isn't really necessary and a waste of money, and I would personally get something like this. (P.S. I personally have a Dell S2716DG and love it.)
Dell S2716DG - $444.70 (Currently on sale and limited stock left)
Amazon.com: Dell S2716DG LED with G Sync 27" Gaming Computer Monitor: Computers & Accessories
www.amazon.com
Or if you wanted to go down on price a little and get the 2017 model that is 24"
Dell S2417DG - $319.99
Amazon.com: Dell Gaming Monitor S2417DG YNY1D 24-Inch Screen LED-Lit TN with G-SYNC, QHD 2560 x 1440, 165Hz Refresh Rate, 1ms Response Time, 16:9 Aspect Ratio: Computers & Accessories
www.amazon.com
And that's for the 1440p stuff.
Here's what you get for 1080p that kind of meets your initial desires but at a lower resolution.
And honestly, you're paying a premium now for this because it's a wonky in the middle option.
It is however an IPS display from LG which is nice.
LG 34UC89G - $749.99
https://www.bhphotovideo.com/c/product/1335260-REG/lg_34uc89g_b_34_21_9_curved_ultrawide.html
And honestly that's about it when it comes to affordable G-Sync.
If we didn't go the route of G-Sync then your options would widely open up.
If you happened to have a 10 series GPU instead, we could've looked into some FreeSync2 options but alas, you are currently on Maxwell.
If you are really looking for something good to play with, I would recommend a standard 16:9 1440p display such as the Dell's I linked.
Then just work on upgrading your platform (i.e. the CPU, Mobo, RAM) and then eventually in the future you can get something like a 1080Ti for a great price on the used market and then you'll be set.
I hope that all of this information was helpful enough to you to help you understand what your options are and where your current hardware sits.
If I'm being honest saying it again, I don't think you're going to have that good of a time at even standard 1440p with that CPU.
The GPU's could handle that if you had low enough graphic settings in the right areas depending on the games so that you don't go over your 3.5GB VRAM limit.
But that CPU is going to hold you back for sure.
You can try to alleviate some of the bottleneck you have right now by overclocking your CPU as far as you can with whatever cooler you have on it, but only assuming you have appropriate cooling on top of it to help support doing so. A stock cooler or something similar to one isn't going to do jack all for you in this department.