For me, condition depends on the year of the cards. Anything 1980-2011 must be PSA 10, 1951-1979 must be PSA 8, 1930's to 1950 must be PSA 4 to 6, Pre 1930's I collect in any grade except qualifiers and authentic's. Pre 1980 PSA 10's I feel can be a waste of money unless money is no object. You can buy 100 PSA 8 1973 Topps commons for the same price as 1 PSA 10 common. I would rather enjoy the 100 cards over the 1.
