Reason 3 On An Imac G5 Options

[alias2005]

Hi there everyone!

Just bought a new iMac 2,1 GHz with 1,5 gig RAM. I bought reason 3 at the same moment and installed it today on my computer, and as well the 3.04 update. I will receive my soundcard next week, but I decided to have a look at the program before that. So I play the demo song that opens automatically in the beginning and what do I recognize... the cpu meter is running at probably 50 % and the program is reacting quite slow.
Does this happen because I use at the moment the integrated sound card that comes with the mac? I have checked out reason at my friends house and the program runs smoothly and with minimal cpu usage (AMD processor).
Do anyone have an answer to this question?