Best sounding Martin

The best sounding Martin is the one I have. GPCPA5K (discontinued) HPL body, Stratbond neck, spruce top Morado fretboard and bridge.
The Only other Martin I've played is the 000M-15 when store manager and I were comparing with martin-designed Sigma 000M-15. WE could not hear any difference.

Very subjective.
Circa 1976, my brother and I shared a 1974 D-18. I lived in Baltimore (Ontario) and he lived in Montreal, so we each played a Yamaha for half a year and the D-18 for half a year.
One day about 40 years ago, I was in my favourite (RIP) music store, Ed's Music Workshop, and I grabbed a guitar off the wall and fell in love. It was 1962 D-21 and I knew after the first tune that I had to have it. I scraped up some $$ and 2 guitars and a Martin bowl back mandolin to trade and 2 days later it was mine. This is my favourite Martin ever and I'll never part with it.

As far as new guitars, there is a new D-18 in the Cobourg L&M store that is very impressive. It blows away the D-28s and everything else in the store. Unlike the other D-18s I've played, this one has an ebony board and bridge and there must be something magic done to the bracing as well, because it's a cannon.

To show how subjective this is, Maggie owned a lovely D-18 before we were married but was never completely satisfied with it. She is just under 5'1" and it was an awkward size. She is also mainly a finger-picker, so she now has a 1921 O-18 that she loves.

troubador, I don't know if you're looking for a Martin specifically, but you sound like your playing style preferences are similar to mine.  So with that in mind, might I suggest you not focus so much on the brand, but the woods.  Try some all mahogany guitars from Alvarez, Taylor, and Martin and whatever other good, quality brands you might have available to you and let me know what you think.

I fell in love with all hog wood acoustics because I love how they sound with my style of playing.

And trust me, there are a bunch of really sweet all Hog acoustics out there to be found.  The only trick is, finding the one that not only sounds great, but that fits great for you too; playability wise that is.

Good luck in your search! 

I remember seeing one with CF Martin on it on a wall in a Guitar Center. Someone else in the acoustic room asked if it was Abe Lincoln... 🙄