I agree with @steakster. I am at 40%.
I was taken aback when I tried some crazy expensive cables with my moderate priced system, Chord Dave and Grimm Mu1 on the front end. Three power cords and a pair of speaker cables. Suddenly it sounded like systems in the $500k+ range.
I fortunately found another brand that was almost as good at a lower price (which many would also call crazy.)
I am now of the opinion that cable and power conditioner upgrades make a bigger impact than most component upgrades.