The flavor of apache hasn't made a big difference on our server, but the latest Linux kernel for 7.2 (2.4.24 or something like that) and the latest version of Postgresql (7.4.2) make it fly.
The kernel fixed problems in the older 2.4 kernels with goofy behaviour by bdflush under heavy load, while the upgrades to pgsql in each major sub rev in the last two years or so have been sweeping in terms of performance gains and sweet new features (like substring with regex, etc...)