Over the years as I have read I have found most all of our Agricultural Schools have been saying soils need 5 percent organic matter. Conversations with many Soil Scientists tell me that comes mostly from knowing that a good loam contains about 5 percent organic matter. In the various soils I have worked in in many parts of the USA and in conversations with organic gardeners all over he world I have reached the conclusion that the 6 to 8 percent level of organic matter is optimal. In the jar test that equates to about 1/4 inch of organic matter floating on top, when the amount of soil put in the jar is 4 inches.
I have not seen that amount change in clay soils, loam soils, or sandy soils, and any organic matter you add will, depending on how active a Soil Food Web you have, "disappear", be digested by that Soil Food Web and will need to be replaced quite often. Since that organic matter is what feeds the Soil Food Web and the Soil Food Web is what feeds your plants that is just a necessary part of gardening.
How much organic matter is needed? Depends on many things, but usually starting with a bit too much is probably better then starting with not enough. The organic matter fills in the voids in your sandy loam which can raise the level of that soil, but probably will not raise the level of the bed 10 inches, 2 inches of compost will probably only raise the level of that bed about 2 inches.

Here is a link that might be useful: The Soil Food Web Primer