Please do not expect any Avalon to sound like a Martin. Trying out a few guitars would be a great idea, it would be like choosing between "oranges and apples" (an old idiom). I believe that you will find a uniqueness that sets Avalons apart from most other brands. They usually have a very even response, with great clarity, although certain tonal characteristics can be emphasized/de-emphasized based on wood choice and body dimensions.
Martin HD28s are usually great guitars, but tend to be a bit more bassy than the Avalons I've played. Try them out if you can, you'll fall in love I'm sure!