Best Laptop to use for CDJ400/DJM400 Setup?

I have a CDJ400/DJM400 setup and have only used CD or USB drive to DJ with.  Looking to get a laptop and Traktor, but wanted some advice on which would be a better laptop to use.  I was going to be looking for a used laptop that may be old enough to work well with this setup, but new enough to still work well and for a while.  I will mainly just use it to store music and run Traktor.  Any ideas?