So I'm close to purchasing a new 15" rMPB and am looking into 27" monitors. I plan to get the 2.5ghz option with the AMD graphics card. I was originally considering the Dell Ultrasharp (2560x1440) but realized that their 4k monitor is only $60 more. My question is, will the 4k monitor be more taxing on the graphics card than the 1440 option?