Logic Express 7 Performance Question

I'm in your usual dilemna over buying an iMac G5 or a Dual PowerMac G5 (not enough power difference in the SP PM to cover the cost of buying a monitor, IMO)

I'd like to be able to do a lot of music creation on it, i.e. multitrack recording, synth work, sequencer, etc etc. Would a dual processor be best for this or do you think I'd be perfectly fine using a program like LE 7 on a single proccessor iMac?

Thanks a lot.