Hi Ed,
I still have my Design Acoustics PS24 center channel. I think these were a solid choice for entry level speakers back then. Mine is still going strong and is a competent performer. Unfortunately, Design Acoustics went belly up some time ago and I doubt direct replacements are available for your rotted woofers.
You may be able to find a suitable replacement on the Parts Express website for a reasonable price. I haven't personally used any of the Parts Express drivers, but many here recommend them. Besides, the Design Acoustics weren't all that expensive when new, so I'm doubting that they used any better quality driver than what you might find in a replacement or DIY quality driver. You may also consider posting the size and whatever else you know about the rotted speakers in the DIY Corner - Tips and Tricks forum for specific suggestions to replace the driver.