One more update:
Upgrading the same box with the same hardware to Redhat 7.1 with the 2.4 kernel saw a significant speed boost again, partly due to 2.4s better SMP support, methinks.

Dinging the same dynamic page of the same site saw page generation rise to 140 pages/second. Damn!!

This may all not be attributable to the kernel upgrade, of course. Apache and mod_perl were upgraded too during the OS upgrade. This boost could be attributed to the persistent DB connections afforded by Apache::DBI, which I've finally puzzled out.

Thought some of you might be interested.