Check collision one cube, sphere or any models in XNA 4.0 3D?

I want to check the collision of one model with another model.I use collision check function as follows:

//Built Bouding Sphere
 private void builtBoudingSphere()
        {
            BoundingSphere sphere = new BoundingSphere(Vector3.Zero, 0);
            foreach (ModelMesh mesh in Model.Meshes)
            {              
                BoundingSphere tranformed = mesh.BoundingSphere.Transform(modelTranforms[mesh.ParentBone.Index]);
                sphere = BoundingSphere.CreateMerged(sphere, tranformed);
            }
            this.boudingSphere = sphere;
        }
//Check Collision
 public bool CheckColision(CModel otherModel)
        {              
            return (this.BoudingSphere.Contains(otherModel.BoudingSphere)==ContainmentType.Intersects);
        }
//BoundingSphere Property
 public BoundingSphere BoudingSphere
        {
            get 
            {
                Matrix worldTranform = Matrix.CreateScale(Scale) * Matrix.CreateTranslation(Positon);
                BoundingSphere transformed = boudingSphere;
                transformed = transformed.Transform(worldTranform);
                return transformed;
            }
        }

The function CheckCollion is great with sphere model but not good with cube or any models because I'm use check BoudingSphere. Can help me check accurate collison? Especially check collision between cubes.