You need to figure out the guitar type that works for you. Do you play with a light touch? Are you mostly a fingerpicking guy? Are you mostly banging out open chords at the nut or do you need a guitar with a cutaway that lets you reach up high for lead playing? Steel string or nylon? Heavy, med, light, or extra light gauge strings?
FWIW, I really like D28s and HD28s . . . a good one just sounds like 'great acoustic guitar' to my ears. They tend to be pretty loud, so you have to learn to control your right hand if you want to sing while playing. In general, rosewood back/sides makes a little mid-scoopiness that makes a hole that works for my voice while singing. But I've found that Martin is wildly variable in sound and play-ability between guitars. Martin also offers a lot of lower spec guitars that I didn't find terribly appealing. If you don't have a place where you can root through a couple dozen of the model you're looking for, it can be tricky to get a one that works for you.
The most consistent acoustic guitar manufacturer that I've run across is Taylor. They are the only brand of acoustic guitar I would risk buying online without trying first. Their guitars tend to all play very well (or can be easily set up to play well). They also tend to be pretty consistent in tone between models. They have a wide variety of guitars, many are smaller bodied and quite bright to my ears . . . but they do offer a few large bodied guitars or wood pairings that give a more traditional/mellow sound. The acoustic that I ended up with is a Taylor 716 - rosewood back/sides, spruce top. It's one of Taylor's bigger body shapes, and can really get the same tones and loudness that I like from a D28, maybe with a little more responsiveness for quieter playing. It has a cutaway, which I use a lot more often than I thought I would. I wish that it didn't have electronics, as I use my acoustic primarily for writing and recording at home and always prefer the sound of a mic'd acoustic to a pickup but they don't seem to hurt the unplugged sound.
Yamaha, Larrive, Guild, and Simon & Patrick all tend to be great value for money guitars worth checking out . . . and I've heard that recent Epiphone stuff has also really stepped up.