Seems like your best bet would be an Intel Chromebook like the Acer C7 - you can easily swap the SSD with bigger one, add RAM and install XFCE/Unity using one of the many options.
It has fans though and you will notice those! And the battery life isn't stellar. But at least it is cheap and relatively light weight and comes with USB ports.
The Acer C720 actually looks quite nice although AFAICT you still can't wipe and install your own OS? You have to use the same methods as we currently have like crouton.
That's right. Something to do with the different type of firmware used in the Chromebooks you couldn't install Windows on them. XFCE on ChromeOS is as close as you'll get.
I don't care about Windows but Chrome OS is based on Gentoo so why the hell can't I just install some other Linux distro like I do on any other computer? It annoys me that it is coming to the end of 2013 and I still can't get the kind of laptop I want running Linux. The closest I can get is the Dell XPS 13 DE but I don't want to run Ubuntu and people I know with them have found getting other distros to work well a pain in the ass. I don't know if things are any better now as I know Dell was trying to improve things for other distros by making drivers more available outside of Ubuntu.
It has fans though and you will notice those! And the battery life isn't stellar. But at least it is cheap and relatively light weight and comes with USB ports.