For Yes get Close to the Edge ,The Yes Album and Fragile (In that order of preference). Best of the Later stuff was probably 90125.
BOC. Agents of Fortune (has dont fear the reaper, the classic track).
You might also start looking at King Crimson if you like this style and sound, followed by Genesis, Van der Graaf Generator and Emerson Lake and Palmer (these bands became Progressive rock dinosaurs and became unfashionable almost overnight when punk appeared, leaving bands like Talking Heads to take music in a different direction).
For my part, I still listen to Close to the Edge and occasional bits of King Crimson. Genesis, VDGG and ELP never get played (although I can still hum a decent Brain Salad Surgery

) and although I dont play BOC, dont Fear the reaper is an enduring classic which rivals Led Zeps Stairway to heaven.