The stable systolic category of a closed manifold M indicates the complexity
in the sense of volume. This is a homotopy invariant, even though it is defined
by some relations between homological volumes on M. We show an equality of the
stable systolic category and the real cup-length for the product of arbitrary
finite dimensional real homology spheres. Also we prove the invariance of the
stable systolic category under the rational equivalences for orientable
0-universal manifolds.