I could almost write a book on the pitfalls of audio production on a laptop, but suffice to say that one of the single most important factors other than computing power is the availability of low latency audio drivers and hardware for whatever laptop you decide upon. And then you enter the jungle of interfaces. Many options exist that work off of USB 1.0 but this is a slow protocol with great limitations specifically in how many audio inputs you can have running at once (usually two) and the stability fo the midi clock. We are on the edge of the coming summer release of much faster USB 2.0 and Firewire interfaces and control surfaces that work with laptops so if you can wait a few more months before making your decision about a laptop/interface and software combo then it may be better. For more info there are discussion topics specific to this subject in the groups at http://www.harmony-central.com.