Which is the most important part of a stereo system?

You hear people say the source? But you also hear people say the speakers. I was a press photographer in College and it's the lens that captures the image on film talking 35mm here. The better the lens the better the image. The body of the camera is essentially a box to hold the film. I would see students in the ’80s and 90s buy the top of the line Nikon for thousands of dollars and shoot with the standard lens it came with.
Eddie Adams the famous Time-Life photographer told me buy a $500 camera and a $2000 lens if you want to capture a good image. I think it's the same with the speakers being the lens and the source being the camera body. Also read that someone was suggested, Marantz I had terrible trouble getting my top of the line $6000 unit serviced after it crashed and burned in the first 12 mo. Has anyone else expended this? I know it's a separate question

It is the SPEAKERS it's an oversimplification this is where the sound comes from. Paul at PS Audio states the same thing.  If you upgrade your speakers you will hear an improvement that should be significant.

If you take a $300 streamer and $3000 streamer most people cannot hear a difference even with a revealing system but with poor speakers, you will not discern the difference.

I think it's like the old SLR cameras the body of the camera just controls the shutter so the money you put into the body of the camera didn't make that much difference a Nikon or pin hole. But it was the Lens that actually captured the image great lens great image. 

Great speakers great sound. It's like what Kevin at Upscale Audio says $40,000 turntable with a $400 cart is a $400 turntable that might be the exception to the rule