multiple css files for multiple themes?

i've seen some older plugins that are to allow multiple css themes to be used on one site..
none of them are compatible with 1.8.
i've seen a demo of a vazco plugin that appears to work, as yet i haven't located it on the vazco site for download or closer inspection.

i'm wondering if there is a recognised (simple) way of altering elgg 1.8+ to support 2 or more css.php files?
my purpose in doing this is to code a css3 special fx style for my site and a fallback lightweight style for visitors who's pc is not up to the processing needed to show the page.