BigGamer, I'd try and get a 120-144hz+ monitor. There are many types from 1080p to 1440p available, from 24" and up. Acer's new Predator series has a 34 inch widescreen that overclocks to 100hz and has Gsync. Gsync from my experience with the Rog Swift Asus monitor and Acer's 4k Gsync is alright, but I would recommend spending the $ on a higher hz/refresh over Gsync if you must pick between the two.
Asus just came out with a new 27" ROG 144hz+1440P monitor to replace the TN Rog Swift with an IPS panel, for about 150$ more, and that's what I'm going to go with I think. I like my current Swift, but the TN panels really aren't that great for color/looks compared to the IPS IMO, and I don't really need pro-level refresh for FPS, and I would rather have an IPS even with the slower refresh rates.
Lots of good options, for under 300$ you can get a 24" Asus 144hz gaming monitor, I've had a 3 monitor setup of these, and they are fantastic for the $. If price is an issue, get that, or the BenQ 144hz of similar price/capability. If $ isn't an issue, the newer Asus ROG Swift is probably the best 27" monitor you can get for gaming, with a slew in the middle. Again, a 100+hz refresh is what you should focus on for any type of gaming IMO, the difference is major between 60 and 100. From 100 to 144 it's a little harder to distinguish, anything in triple digits and you'll be impressed IMO.
Looking at some of Greebo's new skins with my Swift on 1440p from the new Alpha - wow, this is really going to be something when all the lighting/etc stuff and all that jazz is done, and IMO the new AH game will really, really benefit from a higher end monitor as much as a fast GPU.