Andreas thank you a lot! (Ruby script + mini DP to DP) Ruby script worked great for my Dell U2711 monitor. There was no truble with my old Macbook pro 2.2 from 2007 (osx 10.7.5) and this monitor. Full resolution. Although, sometimes it was a bit to much for him. Very resently I upgrated to a Macbook Pro late 2013 i7 (Osx 10.9.1) and it didn't work. Had a old HDMI cable what didn't work. bought a new one what insured me it was a 1.4 type of cable. Little I know that it didn't work for the max resolution. Also bought a adapter from mini displayport to DVI, because I worked on my old Macbook with only DVI aswell. Max resolution was still 1600x1200 I could force for more with SwitchResX app (trial) but than there was a strange scaling in the monitor. For everytime I switched cables I use the Ruby script. In the proces there was always bad rendered text. Only resolution of 2560x1440 is the best. Anyways, the only way to go is the mini display port to display port cable. I read it in this topic (thanks Ryan L and others). Maybe the dual DVI thing aswell but 100+ euro is to much. Mini DP to DP is not commen in The Netherlands in regular shops. You can find many other adapters. I find this a bit odd. Online no problem and for just 17 bucks incl. post. After this I tried to use my Spyder Pro 4 to calibrate the monitor and although Datacolor didn't support Mavericks (they are in proces) It worked. Looked way better. I'm am a bit of an onion about the whole profile stuff and tried to delete the Ruby script result in 'overrides folder' and rebooted. Just to see... Indeed no RGB in the Monitor and a bit of color with my new profile. Resolution was maxed out and good rendering with the text. Now the file is placed back it is shining. Sort of in my head. One thing what concerns me is the mini display / thunderbold port vs wifi fallout.. Some one spoke about it before, up in this thread. While trying mini DP to DVI there was no wifi connection. There was no trouble with my old laptop having internet via wifi. Now with the mini DP to DP I had ones no connection. Ones trouble finding it but found it and a few good ones... Time will tell I guess. Thanks again Andreas best, sorry for my clumsy English. Hope to help somebody with the same, or around same, setup.