Neal, I didn't mean to suggest you remove the spruces. Not sure where to add the magnolias, but I think the smooth round leaves would help with the scale problem of huge house, little meatballs. Filling the spaces between the boxwoods with lilies short and tall sounds cool--what if you used a wide assortment of asiatics, orientals, orienpets, etc, all in white?
There are magnolia varieties that top out at 12', which would give you some layering.
