  We have analyzed the dependences of the threshold value of amplitude of
linear density fluctuation collapsed at the current epoch, $\delta_c$, and its
overdensity after virialization, $\Delta_c$, on matter density content, 3D
curvature parameter and cosmological constant. Though the range for the
threshold values of perturbation amplitude is quite narrow - $1.55\le
\delta_c\le 1.75$ in the region of parameters $-0.4\le\Omega_k\le0.4$,
$0\le\Omega_{\Lambda}\le 1$, $0.1\le\Omega_m\le 1$, the difference in the
concentrations of rich clusters of galaxies (calculated within the
Press-Schechter formalism framework) with real and with canonical values of
$\delta_c$ reaches, and for some models exceeds, 30%. The range of changes for
the overdensity after virialization, $\Delta_c$, is considerably wider for the
same region of parameters: $60\le\Delta_c\le180$. It results into difference up
to $\sim40$% between the X-ray temperatures of gas, as calculated for these
values and for the canonical value of $\Delta_c=178$. Also we have found
analytical approximations of the dependences
$\delta_c(\Omega_m,\Omega_{\Lambda})$ and $\Delta_c(\Omega_m,\Omega_{\Lambda})$
with their accuracies for above mentioned region of parameters being no worse
than 0.2% and 1.7% respectively.
