Considering your goals and price range. I'd recommend shopping the refurb market. Specifically business laptops that are off lease. Bigcorp IT departments tend to cycle their hardware every 3-4 years and flood the market with used cheap/good used laptops. They won't be 'ultrabooks' but they will be cheap, reliable and easy to maintain.
Keep in mind that raw stats/specs aren't everything. I've seen countless people held up by hardware issues that have nothing to do with the speed of the processor.
Something like a Dell E6430 would be a good bet.
https://www.dellrefurbished.com/laptops/dell-latitude-e6430-...?
Keep in mind that raw stats/specs aren't everything. I've seen countless people held up by hardware issues that have nothing to do with the speed of the processor.