08-20-14: AtmasphereVery true. And I would add that the cleaner the recording is, the less loud it will seem. IMO/IME very high quality recordings can be, and will in fact tend to be, played much louder than run of the mill or poor recordings before seeming to be "too loud."
The cleaner your system is, the less loud it will seem.
08-20-14: BombaywallaFor conventional box-type (non-planar) speakers, other than perhaps tall line-source arrays, that would actually be 6 dB per doubling of distance. I can write up a paragraph or two explaining why, if anyone is interested. The number for planar speakers is significantly less than 6 db per doubling of distance, and I believe will vary significantly depending on the speaker's height.
SPL drops approx 3dB for every doubling of the distance.
Addressing the original question, for the classical music which comprises most of my listening I generally find myself listening at average SPLs that are in the 70's at the listening position, with very soft notes being around 50, and brief dynamic peaks on well recorded minimally compressed symphonic music reaching about 100 to 105 db.
Sustained levels start to seem "too loud" somewhere in the 80's or high 70's, for most of the recordings I listen to. Although those numbers would be way higher for something like the "Sheffield Track Record," which I have in my collection.
All of that is at the listening position. I agree that listening distance is irrelevant to the discussion, as is the Wikipedia paragraph quoted above. I'm surprised there is any disagreement about that, especially given the reference in the OP to SPL "as measured from where I'm seated while listening."
Regards,
-- Al