Generally, a laptop with a lot of power would be more expensive than building both your own desktop, and buying an ultra-mobile laptop.  In this case, you would have a desktop with lots of power, and all the right parts, along with a laptop that you can take anywhere.
As a warning, any laptop that can compete with a desktop will be really heavy, really big, and have a super short battery life, so keep that in mind, especially if you want to bring it to class.
The bottom line on laptops, you pay more for less power.