Laptop for audio?

todays dualcore CPUs (i5-i7) should be able to handle any music software you throw at them, quad will obviously do a better job. As with all "creative" type software, you'd do well to get a good amount of RAM for it (I'd say at least 8Gb)
 
The issue you will have is with MIDI quality and play-back as well as interfaces for instuments (if any). You'll need an external sound card in addition to the laptop.