I have a (mid 2011) 21.5" iMac, 2.8 GHz, i7, 4GB RAM, 512 AMD, 1TB HD and for christmas I unexpectedly got a 15.4" rMBP, 2.6 GHz, i7, 512 SSD, 8GB RAM as a gift. Now I don't know weather I should keep both or sell the iMac and buy a 24" or 27" apple cinema display? I will be mainly using for video edit, post production. I can't decide. What would you do?