I would highly recommend the Dell Latitudes E7400 series as I have vast experience with them and the support and quality is there.
http://www.dell.com/us/business/p/latitude-e7470-ultrabook/pd?ref=PD_Family
Alternatively I have used the Toshiba ZSeries as well:
http://us.toshiba.com/computers-tablets/laptops/Tecra/Z50