Logic Pro 9 Planning to run Logic 9 from external HD - any advice


Further to my previous post I cannot get Logic 9 upgrade to install on my main powermac. Disk and internal HD all verified OK, installer just hangs on serial number. Apple care suggested installing the OS and Logic on an external drive - in other words doing a clean install. Are there any recommendations for the HD spec to get good performance - i.e. USB/Firewire, minimum spec etc?