Dave,
This is a little late in coming, but I just now read your post about the difference in a D-50 and a D-55. Maybe I can shed some light on this, for I owned both guitars at the same time.
I did an extensive study on the two, (right after purchasing the D-55), comparing them side to side; picking one up, playing it, putting it down, playing the other, going back and forth.
The '93 D-55 had a warmer, richer sound, felt majestic in my hands. It also had, to my dismay, lower frets than the 50. This meant that more contact was made between my fingers, and the wood. Some people like that, I didn't. The '82 D-50 had higher frets, which helped in my playing, was (rather, is) a little brighter, more "alive" sounding, and had a little less "majestic" sound and feel to it. It lent itself to more inspiration to play, more so than the D-55.
It was almost like the D-55 was too much guitar for me, and that playing the D-50, the one I had since new in '82, was like "coming home".
I talked to a few of my guitar repairmen, asked about refretting the D-55, giving it higher frets. At a cost of about $350 - $400, I decided against it. That was my main issue with the D-55. Other than that, I enjoyed it. But not as much as my D-50. And seeing that I had paid pretty much top dolloar for the instrument ($1800), I decided to unload it for something I would really enjoy. (And that guitar is up there on the left
)
I ended up selling the D-55 to one of the guys in the acoustic guitar ensemble I had at the time, and he was more than happy to take it off my hands.
So, the D-55, warmer, louder, richer, more "regal".
The D-50, brighter, still just as loud, a little bit more "jangly", not as "regal" as the D-55.
But each person has their own tastes, it is all up to the individual.
I see a lot of D-55's on Ebay at all different prices. Should be no problem picking one up. Same with the D-50. But stay away from the Corona built models. I have played them, and the sound is just not there. Not even the D-50CE, which is a cutaway acoustic-electric. They sound even worse.
Now, if you want something really good, the new Tacoma-built D-50 is the one. If I lost my '82 D-50, I would waste no time in picking up the new model.