I bought a used 13" MBP from 2011 with Intel's i7, 2.7 Gb and Intel 300 512Mb graphics card. Following the ongoing trend among my peers, I decided to upgrade the RAM and HD to 16Gb and SSD respectively. Adorama did it for me actually. Ever since, even though my comp is booting very fast (about 20-30 sec) I did find it strange that: 1-When I transfer files from SD camera card via built in SD slot or from external SD/CF card reader, or if I transfer files from one external HD to the other (regardless if its USB or FW800) it rapports unusually long transferring times (2 hours for 45Gb). 2-When I preview video files (HD or 4K UHD), or even if I play them through QTPlayer, VLC, FCPX 10.2.3 or Adobe Premiere 2014 CC, it stutters and plays it choppy. The thing is that, before the RAM, SSD and OS upgrade, these files were played normally without and jerkiness and stutter. I did some research online but can/t figure out what could be a problem SATA Cable? How can I be sure it is that? SSD incompatibility? But it seems like the one I have is a proper one. OS? Should I downgrade t oYosemite? Should I upgrade to Sierra? Graphics Card is not up to the task? But then, Why would it play it normally with less RAM and inferior HD is its a bout the graphics CARD. How can I nail it what is a potential problem?! TIA for any kind of gudanance!