  We examine the prospects for measuring the dark energy equation of state
parameter w within the context of any uncertain redshift evolution of galaxy
cluster structure (building on Majumdar and Mohr, 2003) and show that including
the redshift averaged cluster power spectrum, P_cl(k), and direct mass
measurements of 100 clusters helps tremendously in reducing cosmological
parameter uncertainties. Specifically, we show that when combining the redshift
distribution and the power spectrum information for a particular X-ray survey
(DUET) and two SZE surveys (SPT & Planck), the constraints on the dark energy
equation of state w can be improved by roughly a factor of 4. Because surveys
designed to study the redshift distribution of clusters will have all the
information necessary to construct P_cl(k), the benefit of adding P_cl(k) in
reducing uncertainties comes at no additional observational cost. Combining
detailed mass studies of 100 clusters with the redshift distribution improves
the parameter uncertainties by a factor of 3-5. The data required for these
detailed mass measurements-- assumed to have 1sigma uncertainties of 30-- are
accumulating in the the XMM-Newton and Chandra archives. The best constraints
are obtained when one combines both the power spectrum constraints and mass
measurements with the cluster redshift distribution; when using the survey to
extract the parameters and evolution of the mass--observable relations, we
estimate the uncertainties on w of ~4% to 6%. These parameter constraints are
obtained from self-calibrating cluster surveys alone. In combination with CMB
or distance measurements that have different parameter degeneracies, cluster
studies of dark energy will provide enhanced constraints and allow for
cross--checks of systematics.
