I am far from an expert on Apache or any server for that matter, so i apologize if this question is poorly worded, which it likely is.
We have always relied on a vendor for split-path testing (aka "AB Testing"). If you're not familiar with that term, it's a form of marketing research in which you slightly modify one of your web pages (usually one nearest the point of conversion), say for instance, by changing the position of the "Buy Now" button or its color/contrast/texture, then serving one of those two pages to a given user based on random selection.
By doing split-path testing ourselves, I suspect we can do it far more cheaply and increase cycle times as well.
What is the optimal set-up for these tests? "Optimal" is based on the following criteria:
how quickly/easily new tests can be set-up and put online; and
minimal disruption to overall site performance