The absolute best thing a Male with any of the names above (or variations of) can do is to get a Y-DNA test!
People can debate, compare papertrails, brainstorm and conjecture - but the only absolute certainty of your lineage is contained within your body.
If every male would get at least a 37 marker test at FTDNA.com and join the groups of Calhoun/Cahoon/Colquhoun and Kirkpatrick/Kilpatrick we all would learn so much more about our roots.
I would like to see all males of these surnames do this test. Ladies, encourage your fathers, brothers, uncles, nephews, cousins, etc. to do this and we can all get some definitive answers to our questions!
I paid for my nephew to take the test and we have found matches not only here in the USA, but also in the UK and in Australia bearing the names of Colquhoun, Kilpatrick and Kirkpatrick.