I haven't seen the list on OwlSpace yet (submitting my deposit tomorrow), but the requirements in the admissions binder/FB group aren't anything special. You could get a decent laptop for about half of the $2k allowance. 13.3" or 14" models were highly recommended in other b-school discussions - primarily because we will be lugging them around a lot. You can always plug in a desktop LCD when you're at home.
Look at the Toshiba Portege and Tecra lines, Lenovo Thinkpad T and X lines, or the Apple MacBook Pro (with Bootcamp or Parallels). You want a sturdy business laptop and not a low-end consumer model (these tend to fall apart/fail after serious use, especially the keyboards and disk drives). Plus the cheap ones have lousy QA, meaning you may find yourself trying to RMA your laptop in the middle of Immersion.
Otherwise, regular laptop purchase rules apply. Spend money on memory before processor speed - 4GB memory + a basic Core i3/i5 will do just fine. Also, go to a store and try out the keyboards - you will find that some keyboards just don't work with your hands.