mike, comparing the stereo abstraction i posted above with the freeverb~ external:
the abstraction is way more economic than the external. (less than half the cpu usage on intel mac)
if you want to do the test for yourself, all you have to do is go into 'media' in the pd menubar, and select 'Load Meter'.
then make a new patch with multiple copies of the object you want to test. keep making copies of that object until the cpu usage hits about 50%.