Generally speaking, any laptop with an Intel Ivy Bridge Core i3/i5 CPU or AMD Trinity APU should do. Streaming video is not very demanding on the CPU or graphics core.
Your primary limitation will be your internet service. It must be able to download fast enough so that video does not stutter. I think the generally recommended minimum download speed for HD Video streaming is 15mbps or 20mbps.
There is a laptop FAQ thread that you should fill out so that people can help you find a suitable laptop.
if your not going to game with the pc then the 300-400 all in one hp/dell's will work. if you want a pc you can game with then build a unit with an i3 or amd cpu. may be a little more money but the pc have better parts.