I've just been trying out a relatively inexpensive upgrade to my vinyl set-up that has impressed me greatly. I suspect the biggest improvements are to be found with lower-end set-ups, but my experience, with a reasonably high-end vintage set-up, has been extremely positive.
It's an isolator of sorts, that fits between cartridge and headshell, made by the Funk Firm in the UK (formerly Pink Triangle), known as "Houdini".
It's resulted in a lot more depth, space and resolution to the music. What was a bit of a mellow-sounding cartridge seems to have more bite/attack and firmness in the bass, without any harshness.
The cost in the UK is £300, which many commentators on various forums have written off already, despite not trying it, purely on the basis that nothing this small and simple should cost this much money. The entire HiFi arena would be a very small place indeed if everyone believed this!
There are actual reviews starting to appear from sources with more knowledge and experience than I. Houdini will soon be available to the public (FYI: mine was supplied and fitted by Arthur Khoubessarian of the Funk Firm and I paid full price for it). I understand that they're offering a full money-back guarantee to buyers who try it and don't want to keep it.
j.
System:
PT Tarantella/Origin Live Silver/Ortofon Kontrapunkt B/Houdini
Audio Research SP9 mk3
Micromega Solo
Albarry M1008 Monoblocks
Pro-Ac EBT
(VdH/Kimber/Cardas cables, Woodblock/Red Rollers RF inhibitors)
(my primary turntable - PT Too (Anniversary Spec)/SME V/Koetsu Urushi currently out of action)