NiCoM :
If you play alot of FPS games then you'll want a 120 or 144hz monitor, though they have the downside of having washed out colors, probably even compared to your current monitor which is a IPS panel.
If you play alot of rpg/action, not so much FPS, then i would recommend going for a 1440p IPS panel monitor (they only run 60hz and is also all you'll need with a single gpu).
So the 120/144hz is going to give you an extra edge in FPS gaming after you've "adapted" to using it, though it will give you much worse color fidelity. The 1440p IPS on the other hand would give you a nice, more sharp picture to look at and the 60hz that you'll need for any game.
Much worse is a little strong IMO. it is true TN monitors colors will be slightly washed out vs a IPS monitor. If you play alot games and are getting into it you are not going to be able to tell. However if you do alot of photo editing thats where you will see the difference.
I absolutely love my ASUS VG248QE 144hz monitor, I play just about every type of game BF4, Skyrim, Metro, ESO, ect. Maybe it is just me but when I am gaming I don’t sit there like OMG that red is slightly lighter than it should be, I get into my games and I would rather have a butter smooth game play, just about zero input lag, with fast response times.
You said you are going to get a r9 290, I would get a fast TN panel vs IPS. The 144hz is amazing especially for FPS games, you see more than twice as many images, your targets movements are more fluid and you shoot where he is vs where he was (it makes a difference). Once you play at 144hz you will never want to play at 60hz again. But that is just my opinion, it really comes down to what you preference is, and how you like to play your games.