I and friends of mine had an amazing trekking to the Everest base camp organized by the Breakfree Adventrues Company. We checked many agencies in Kathmandu and on internet before deciding for it. We choose Breakfree Adventures because of their price are highly competitive and the response of our email from them is very promptly.
The staff is very competent, professional and fluent English speaking.
We definitely recommend Breakfree Adventures for organizing your trekking!