I went with 'The Adventure Company' they do a bunch of hiking trips in Nepal. The one I did was the Annapurna sanctuary trip, though there are others including the longer Annapurna circuit and the Everest base camp one.
There should be prices for different times of year on the website.
As for whether I recommend them, I don't really have other experiences with other companies to compare with, though everything seemed well organized and I had a great trip.
Also as the intended flight in the package was full when I booked, meaning I was put on another, I ended up getting an extra couple of days in Kathmandu before the rest of the group arrived, which was great as it gave me a chance to have a good look around and acclimatise. (I'd perhaps recommend doing so intentionally)
Good luck with whatever you may plan.