Are you making a song or rendering Avatar?
What's always worth more then an extra ghz of processing power is the ability to change our production environment. Unlike game production, music production is hardly limited by hardware capabilities. It is limited by creative capabilities, which I believe is strongly affected by work environment. If you have the desire to max out fl's 100 tracks loaded with every ozone plug-in you can think of, go ahead and buy your 8-core powerhouse, but for what I would conisder the average bedroom/hobbyist an average dual-core laptop with 4 gigs of ram is an excellent amount of power when used correctly. You see more and more musicians simplifyinh their setup using just a macbook pro and headphones, of course sending it off to a very well equiped studio for mastering, but I think they work fine on their day to day mixes. The point is if the likes of Madeon or Zedd don't need the latest workstation, it's very likely neither does yourself.
Can I get a change of view please?
I don't know if this is just me, but I easily get sick of my surroundings and a desktop doesn't like to accomodate this. As I have already stated you can put a price on processing power, but your creativity there is no price (Ok $10 to get high on lsd..) so why would you limit yourself to the same wall and desk. I travel a fair chunk so it makes sense to have somthing mobile, but the inspiration that can occur when you are out of your ordinary work space can be priceless. Sometimes the moment just strikes.
So with notebooks great price point these days and the priceless attribute of mobility, this is why I think you cannot go wrong.