Best Bang For The Buck I've Ever Spent

Original Japanese promo records from seventies and early eighties. It's as if you'd just upgraded your entire system. Played with the same arm and cartridge, of course. Forget the fancy arms and cartridges to begin with - get the recordings in the best quality available. Yup, master tape dubs would be better, this is second best.

Chrod Mojo

It was either the Shure V15 RS I bought new from Radio Shack in 1985, I think for less than a replacement stylus for the V15 III I was using; or an Oppo DV-980h I bought in 2015 for $85 shipping included just to see if I'd like SACDs. Turns out I do! DVD-A, too; and a few of the CDs I already owned had HDCD layers and I never noticed.
I still have 2 V15 RSs and use them a lot. The DV-980h has been moved to my den system and replaced by a BDP-95 in the main system. 

Don't forget real live plants (not silk ones)

Speaking of plants and flowers and, yes, I realize I’m directly contradicting the previous poster, but plants and flowers actually hurt the sound. They hurt the sound simply because they are in the room. Not because of any of the usual acoustic theories. All flowers and plants should be removed post haste. I know what you’re thinking, "but plants are natural and act like diffusers." Well, they don’t really act much like diffusers, and it’s because they’re natural that they hurt the sound. If you think they improved the sound it’s most like a simple case of expectation bias. I suggest maybe an A/B test is in order. Are plants and flowers controversial? I guess we’ll find out soon enough. 😀