As for gaming, it comes down to the game you're playing. In Twitch shooters like CS:GO, or fan favorites in Overwatch, League of Legends, and other massive hardcore games, 165FPS makes a big difference, but only from 120Hz.
If you've got a 120Hz monitor but at the 1080p native res, you'd skip over the 144Hz monitors and dive right into the ViewSonic XG2704-GS with its 165Hz refresh.
Moving from a 1080p 120Hz monitor to the 1440p 165Hz is a big upgrade on the visuals, but it also requires much more GPU horsepower. You could've gotten away with an older GTX 980 Ti with games like CS:GO and Overwatch at 120FPS at 1080p, but at 1440p and 165Hz, you're going to need a GTX 1080 or Titan X at least.
Multi-GPU is where it'll be at for the future with 4K 144Hz, as it's not going to be easy to do 4K at 144FPS minimum on a single-GPU anytime soon.
PRICING: You can find the ViewSonic XG2703-GS 27" 165Hz IPS WQHD 1440p G-Sync Gaming Monitor for sale below. The prices listed are valid at the time of writing, but can change at any time. Click the link below to see real-time pricing for the best deal: