Good, put more thought into because it your money you're dealing with. One other thing to think about. Okay, so you'll ship the iMac to OWC to get the SSD and HDD upgrades. What happens if comes back with a few light scratches on the casing or there's dust under the screen? At that point it will be a PITA dealing with OWC to take care of these problems and although dust under the glass is not major, they may try to argue with you about the scratches. Whatever you do is your decision but it's good that you came here for opinions.
