HI, I have iMac 27” mid 2010 2.8 ghz intel core i5 8gb 1333 mhz ddr3 Ate radeon hd 5750 1024 mb After installing to high Sierra, editing photos takes too much time, and stop response sometime. It happen espeailly when I edit Raw format file. So I'm thinking to upgrade my iMac. Please let me know which upgrade (Ram/SSD/...) is good choice! Thanks.