Unfortunately most computers these days are coming with Windows 8 and most people either can't stand the new look/feel or are unfamiliar with it which makes for a shaky user experience. If that is a problem, I would recommend sticking with the Asus you had originally mentioned. I have an Asus netbook and I love it. Asus is a good brand so it's not like you are going to get a piece of crap. If Windows 8 isn't a problem, then you can get cheaper, better spec'd laptop from Dell or HP. See the links below. I would try to stick with a 64bit OS (as it is more versatile), at least 500GB of hard drive space, 4GB+ memory, and a dual core processor with at least 2.4GHz+ processor. With Intel, the higher number "Core i3,i5,i7" is simply a better processor as you get higher in number, but also increases in price as well. For a $550 limit, you are pretty much looking at Core i3 and maybe entry level Core i5 (if you are lucky).
On a side note, I tend to get a set of specs that I am looking for, as well as a price, and go to each of the major manufacturers websites and look to see what computer best meets those specs. I think take each one of the models from each manufacturer and compare them using either Excel or just looking at each webpage side by side. Once I narrow it down to 2 PC's I find the differences and see what I am more willing to live without and choose that model. I just find this the easiest way to do this as there are soooooooo many different models out there it can get overwhelming.
Dell:
https/www.dell.com/content/topics/segtopic.aspx/inspiron-laptops?c=us&cs=19&l=en&s=dhs&~ck=mn
HP:
http/www.shopping.hp.com/en_US/home-office/-/products/Laptops/Laptops?SearchParameter=%26%40QueryTerm%3D*%26categoryusagelaptops_dte2%3DHigh%2BPerformance%26CategoryUUIDLevelX%3DjeEQxXjbj14AAAE0syxcZzOW%26%40Sort.TieredPricing%3D0&ShopByUse=High+Performance