The way I understand the story is...
The collectors dream guitar is a pre-war Martin.  These are guitars made before WWII.  Back then, Martin had the X brace, which is behind the front of the guitar, closer to the sound hole.  This gave the guitars a distinctive sound.  The problem was, because there was less bracing under the belly of the guitar, over time the belly would poke out from the pull of the strings on the bridge which wasn't always a bad thing but customers looked at it as a defect.  Martin then moved the X brace back towards the belly a little to prevent this from happening but doing this changed the tone of the guitars, not to say that newer Martin guitars sound bad.  Because so many guitarists want these old guitars and there aren't that many to go around or they're too expensive, Martin has come out with a "Vintage Series" where they have gone back to the old pre-war style.  I've played a few of these.  They sound great.  Hopefully someday I'll be able to try an original old pre-war Martin to see what it's all about. 

Bob, Gman ( o )==#

X Brace