  We use the framework of a recently proposed model of reduced relativistic gas
(RRG) to obtain the bounds for $\Omega$'s of Dark Matter and Dark Energy (in
the present case, a cosmological constant), taking into consideration an
arbitrary warmness of Dark Matter. An equivalent equation of state has been
used by Sakharov to predict the oscillations in the matter power spectrum. Two
kind of tests are accounted for in what follows, namely the ones coming from
the dynamics of the conformal factor of the homogeneous and isotropic metric
and also the ones based on linear cosmic perturbations. The RRG model
demonstrated its high effectiveness, permitting to explore a large volume in
the space of mentioned parameters in a rather economic way. Taking together the
results of such tests as Supernova type Ia (Union2 sample), $H(z)$, CMB ($R$
factor), BAO and LSS (2dfGRS data), we confirm that $\La$CDM is the most
favored model. At the same time, for the 2dfGRS data alone we found that an
alternative model with a very small quantity of a Dark Matter is also viable.
This output is potentially relevant in view of the fact that the LSS is the
only test which can not be affected by the possible quantum contributions to
the low-energy gravitational action.
