1-5ms is unnoticable for nonPro players, the lower is better obviously but it doesnt make any noticable difference. U can buy 1440p 120/144Hz and depending on game settings or games (LoL, CSGO, Dota, Overwatch) u might get 100+ FPS. U will surely keep that monitor for your next upgrades and when u do upgrade u will take full advantage of its refresh rate. The question is if u have budget for Gsync and if Gsync will be relevant in 2-3 years. I personally dont know much about Gsync and therefore cant say whether its worth it or not.
I own a 144Hz monitor with a card that cant provide 144Hz in all games but I dont notice any screen tearing in the games I play (H1z1, BF4, LoL, CSGO, Overwatch...).
Would you say this monitor is ok? I had to cut my budget so I can´t afford a 144Hz one. Its an 1440p, 60Hz, 4ms response time
https://www.amazon.com/Acer-G257HU-smidpx-25-Inch-Widescreen/dp/B00QS0AKVK?ie=UTF8&keywords=Acer G257HU&qid=1448523787&ref_=sr_1_1&s=pc&sr=1-1