You're right. here is my suggestion.
Your hardware - Nvidia gtx 970, I5 4690k
Choice of game types - All
prefered resolution and size - not specified
Panel type - Not specified
Gsync/freesync - not specified
Straight away, I can tell you that you should be looking at 1440p resolution. Your set up will run most of the modern games quite well and in the future, if you pop in a second gtx 970, you can run the future crysis 4 at max and 60fps.
Next thing is the screen size. At 1440p, a 27 inch screen will give you that perfect pixel density which imo is the sweetspot for quality/hardware required. If you were going 1080p, I would have recommended a 24 inch instead. but with 1440p, It would be a shame to not go to 27 inches and enjoy that immersion.
Last is that type of monitor. Sitting in Europe, I converted the price range you were looking at to 400 - 450 euros. so within that price range, you have a decent amount of choice.
If a little extra response time doesnt bother you, You should look at IPS panels instead of TN panels since they give you a superior picture. If thats the direction you wish to take, I can suggest this one -
BenQ GW2765HT : Its well reviewed, has a good picture and good build quality with having an IPS panel 60hz with a 5 ms response time.
If you are succeptable to slower response times and you need that blazing speed, you have the option of something like the Acer G277Hu- Though I cannot recommend any TN screen at 1440p resolution except the Asus ROG Swift. The reason for this is because apart from the ROG Swift, the rest of the TN panels have 6 bit native color. The rog swift has an 8 bit native color giving it that surprisingly good picture quality. However, The ROG swift is more expensive and If you are going to go this route, I have to recommend a different monitor -
If money no object and you are looking to spend ROG swift kind of money, get this - Acer XB270hu. This is the perfect monitor (yes that exists now). Its as fast as the swift and its IPS.
Your card is plenty to enjoy a good game on this monitor. What you need to do is to first max out settings and then drop it slowly till you can get above 40 - 45 fps. You'll probably not play crysis kind of games at max, but trust me, gsync at 50 fps is very very fluid. Ofcourse, later on, you can always add another 970 or when you upgrade your card a few years down the line, you might be able to play at over 100fps. The important thing to keep in mind is that this monitor can handle your next gpu upgrade. It is a long term investment. a 60hz monitor even at 1440p might be too little when you upgrade your gpu maybe a couple of years down the line.
