For Linux purpose also, i never buy newest models! You never really know, if the kernel will support all the devices on that notebook. I prefer Lenovo Thinkpads for their Linux capabilities, their matte displays, their keyboards and their overall sturdiness.
On Ebay you could get refurbished, formerly leased notebooks from two years ago, that barely have any traces of use, for a decent price below your budget. There is enough testing done from Linux users around the world to single out the less working models, if there are any.

Personally i tend to use their 12" tablet pc line, to use with stylus digitizer, touchscreen or touchpad. But those are a little bulkier than most modern notebooks.