I want to buy a MacBook Pro 15 Retina early 2013 with 16GB of RAM, I have a hard issue in choosing a processor i7-3840QM and i7-3740QM, please tell me they have a difference in the 0,1 GHz and 6 or 8 Cache. I will use very often on Parallels with Windows 7. I do not work with graphics software and video editing, but it will be very hard-loaded my Parallels other software. Tell me please, I really need your help in choosing the configuration. PS: I had a sad experience with Parallels included in unit 2012 2.6GHz and 8GB of RAM, I had to sell it due to the fact that expand the RAM failed in this model MacBook and very much caught bugs in Windows Parallels.