I work from raised beds as well, and 2cu sounds about right (i don't have my journal handy to confirm) but in a 4x4 raised bed, and I use 2x8s filled to six inches, that means there is 2 cubic feet of planting (4 sq feet/2). Yes, that's right;)
My soil planting mixture is the old Mel's Mix from the square foot gardener series on PBS:
1/3 peat moss
1/3 compost mix, and that mixture contains at least 3 different types, in equal proportions.
Here in NH, the simplest to pick up are seaweed, cow manure, and blueberry. My own compost bin is for enrichment, not initial bed 'seeding'.
This mix is self sustaining in its design, as the peat moss helps retain moisture, the vermiculite aids in draining excess water (never over water again:), and the mix of compost makes sure I don't have too much of one nutrient, and not enough of another.
I have grown a variety of crops in this mix, starting with lettuces, beans and peas in the early season with great results, followed by summer crops like toms and peppers, corn and the like (yes, you can grow corn in raised beds), and squashes in the late season. All came out amazing...
Yes, these are my budding lettuces in the mix.