[eMacMan]

...Trying to change any aspect of the chart spiked one of the processors at 100%, and caused the whole application to become non-responsive for at least 30 seconds....

Switching over to Excel for now.

Seem to remember a similar issue with ClarisWorks Spreadsheets on my LC475. I turned off the "Auto Calc" menu item and when all my data was up to date clicked on "Calculate Now" then took a bathroom break.

Does Numbers retain that useful feature?