That is a bit strange! So the plot thickens again. Clearly there is a Kinch /Inch by Gorey connection with your part of the world from that tombstone I found, and the shipping list entry I sent you, but without the Utah evidence there is no concrete evidence to connect Lawrence's line to that place! Does he or any of his Irish Born family appear on Canadian censuses with a Birthplace?. I'll have a look at the LDS again - I could not find him and I think I got all the Kinches, but I restricted the search to Wexford.
I have had a similar problem with a nice family in the US who are convinced they are my relatives, but although they went from here to the US and have the right surname and parish, there is no documentary way that I can see to prove the link, even, as in this case, there is only one family of the name in the parish. They are convinced my gggggfathers house is the "homestead" and go there every few years and we meet up!
See Ancestry have generated one of those odd books:
http://www.amazon.co.uk/gp/product/B001KZLXO6?ie=UTF8&tag=ounainhi-20&linkCode=as2&camp=1789&creative=9325&creativeASIN=B001KZLXO6And to add to the confusion - Here is what the OUP has:
English: of uncertain origin; perhaps a shortened form of Kinchen.
Irish: reduced form of the Gaelic patronymic Mac Aonghuis ‘son of Angus’ (see McGinnis).
Anglicized spelling of South German Kintsch, a variant of Künz (see Kuntz).
Dictionary of American Family Names, Oxford University Press
On the more general question, I do generally rely on McLysaght - he is a much respected source. The passage you quoted about Saran is probably derived from one or other of the Irish Annals or old genealogies, and were written long after the event. This is a complicated area of study, depending on the source - we are in the hinterland of Irish research here, where myth meets history!
However, perhaps Wendy may be able to give us the sources for the House of Names research? That would be really helpful and might broaden our search.
I have never thought of doing a one name study, so there are probably lots of ways of finding out about the Kinch origins I don't know about - and it is fun!