Quote Originally Posted by DSP
a good sound card helps this situation a lot.

what sound card do you have?
are you using the ASIO drivers for it?
increase your latency/buffers on it.

at 70% cpu and studdering it sounds like your latency is either too low or you're using the wrong drivers.
Yeah sounds like a POS sound card to me. 70% cpu on a 3.2ghz P4 with half a gig of ram is nuts.
When I run Logic or Live I constantly have 10-18 tracks running all with 5-6+ chained fx, some of which are Waves... and my cpu may hit 70% at times... but it never ever studders.
I have an Athlon 2100+XP (1700mhz), Echo Layla 20 8in/8out interface (ASIO drivers), and 512MB ram.
There are other factors of course that could play into the reason why you are getting studdering (such as disk like ZeMigL mentioned...) but from the sound of it the box is decently beefy.

-Chris