In OS9 if you had a lot of memory you could create a ram disk and work all your audio into that. Ram is a lot quicker than the hard drive, though you must remember to save your work to a real place before quitting otherwise
or
occurs! This should lessen the burden on the hard drive. If you could do 7 audio tracks in ram and still have the same problems then you would be out of CPU with the effects you're using.
Can you get more than 7 tracks without effects?
I don't know if you can do ram disks in OSX. I haven't looked into it.
But it is nice to have metro in a more stable environment than OS9 and OMS and not having to worry about when the machine is going to lock up next. (I think under 9 I used to run too many 3rd party extensions ready to hang my computer at any chance they could get).