Need some laptop recommendations

You can do with $400. It's just not going to be worth it. Push it to $500 at least. You can touch dual cores with $500. With $400, even a really good single core can't compare to an average dual core. Also, stay away from netbooks. Their CPUs focus more on power saving than performance so you lose out on performance. Every laptops comes with the standard 802.11b/g/n wifi so you don't need to worry about that. Walmarts carry cheap laptops but in exchange, most of their laptops suck. Hardware problems.