I've come across and played a fair number of acoustic guitars and would like to make the following observations.
The condition of the strings is paramount, a fairly obvious thing to say, because, as we all know, the string provides the initial sound. Why then do we see guitars strung with ancient bits of unresponsive fuse wire? If you are thinking of paying £1000 for a guitar, when you have it short listed, put a brand new set of your favourite strings (costing less than £10) on the thing and try it again, it may save you £990.
The make of the guitar is a general guide only, you get bad ones from the best makers and decent ones from the cheaper end of the market, give the instrument a good look over before you buy/reject it.
Martin and Gibson guitars are generally overpriced crap in my opinion. Look for an old Vega for a good cheapie.