Look for Dell S2716DG, Best Buy in US had it on sale 2 weeks in a row for $360 US. I paid around $400 at MicroCenter for mine.
I have had this monitor for almost 3 years now. 27”, 1440p, 144hz, 1ms in Fast mode (which i dont use), and gsync. Plus the stand and extras are high quality, looks professional (which i like), and has a 3 year warranty.
The knock from others will be it’s a TN panel, whereas IPS is usually what people swear by... I think this price vs quality of the Dell make it a solid option.
I even used it with a 1070 ftw before I upgraded to a 1080 ti, looked great on the 1070.