The problem with laptops is their compressed bus system (the data lanes that pass data between the various components of your computer) in contrast to a desktop computer. Dollar to dollar comparison, you'll afford a desktop computer that's twice as fast given the same budget. That said, if you must use a laptop, then you shouldn't buy anything less than an Intel Core i5 (or comparable) with as much RAM as you can afford. For normal everyday use, you'll seldom need more than 4gigs of RAM but for Audio/Video recording and editing RAM capacity counts!
my laptop of choice for right now is the Asus K53e. Its discontinued, so i got it for a really good price (350 cash with 169.00 store credit for a trade in). Its mainly my on the go, oh I want to make a beat but Im not at home machine, plus its for college. So like, while Im out, I can get insipiration or whatever, lay it down, make a decent beat then transfer the project to my more serious desktop.
It doesnt have the best performance, but its got two i5 processors and i think 6GB of Ram so its not bad. It might even only have 4, but like i said its just a on the go machine not the heart. But if i NEED NEED NEEDED it to be, it could get the job done.
When my old laptop took a dump, I went all out and got another PC laptop. MSI gaming laptop, i7, 8gbram, noreflect screen, THX sound system. Cost the same as a mac. Does exactly what i needed to do.