Like most here we all have our brand of mower and will tell you why they like their mower. I prefer Exmark mowers. Especially when you get to residential with commercial options added and commercial mowers. I feel the quality and detail are better in my opinion. Be sure when you compare mowers you are comparing apples to apples. All the name brand full on companies (Exmark, toro, gravely, etc) have residential, the in betweens, and the commercial mowers. Price goes up as you go form residential to commercial. The price range you have given would the residential Exmark Quest (
Exmark Manufacturing - Products) E or S series 2999 to 3999 in most cases. At 5000 you can begin to look at the in-betweens/commercial series. For Exmark, that is the Pioneer Series (which is what I decided on a couple months ago) and the Lazer series (Lazers are commercial). I would also suggest you consider the dealer who will service your mower. Are they local? Do that have a good reputation? Are they timely? etc. This was a big deal to me when I bought a couple months ago.
Take your time and do your research. With just an acre, you don't need overkill, but you do want quality. You are making a potential long term investment with good care of the mower.