Hey toms! Here's my take on your dilemma. A lot of classical guitars come with cedar tops, which are very light and responsive, and could account for the volume that the Yamaha was throwing, if indeed its top was cedar. Of course, the 814's top is spruce, and not knowing if the new 814n's have the new thinner finish of the other 2014 8 series steel string guitars, I wonder if its just the fact that the top is a little tougher to get going than cedar. Also, not having a second 814n to compare to, it's possible that this particular model just didn't have "it." It's happened before, but thankfully with Taylor, those are few and far between.
At any rate, I wouldn't be too hasty to dismiss the 8 series for a nylon guitar, but if I had my druthers and it was volume I wanted, I would shoot for the 5 series with a cedar top, if indeed Taylor offers it in a nylon version. My 514ce cedar top steel string can really throw some volume finger style...