I have 2 of the top link cards in your OP in one of my systems. For the $ the 970 is one of the better cards to come along in a long time. Two of them = a better deal than a single 980 for games with good SLI profiles. Be warned that they do NOT overclock all that great, but it isn't a huge issue - some have gotten into the 1400 range but 1380 is the norm, and all I could get out of either card as well. IMO the G1 is probably the best option for the $, they just weren't available when I got mine when the 970 were released on day 1. Good comparison review here
http://www.overclock.net/t/1516121/gtx-970-comparison-strix-vs-msi-gaming-vs-gigabyte-g1So far as a monitor goes, if you're looking for a 27", I would try and find one with a bit better than 5ms gtg, if gaming is your main priority. If it isn't, no big deal. There are better 27" IPS options out there IMO, and far better gaming TN panel ones as well. Some of the Korean models you can get now are in the same price range as the model you're looking at, but give you 120hz capability instead of 60, and are very clear IPS panels, in addition to being 1440p instead of just 1080p, so don't overlook them while checking about. The other option is if you're focusing on gaming, to look at 120 or 144hz 27" models as well. Both BenQ and Asus make several, and they come on sale in the low 300, sometimes even higher 200 range if you watch. With the Korean imports you can have both 120hz and IPS at 1440p right now for 300ish.
These links are from a Canadian site, but give you an example of other TN gaming panel options.
This is one of BenQ`s 120hz gaming monitors, that you could get for 270$ USD right now if they didn`t sell out.
http://www.memoryexpress.com/Products/MX48351This is just one of many examples out there, IMO there are better options for a sub 300$ 27" monitor than the Asus in your link. Nothing against Asus, I have several of their LCDs myself, it's just that particular model isn't going to be the most optimal you can get for your money, particularly if you're going to be gaming with it. It is also personal pref, some prefer to have an IPS panel over every other consideration, while some prefer to have higher fps/hz capability with the 120/144hz options out there, and so on. Either way, again, there are better options for your $ out there than that refurb 5ms model.