The author has seen at least half of these possible spellings in print at one time or another. A spelling beginning Qua- is also sometimes seen; in English, this would be incorrect, since it would imply a pronunciation of kwa- instead of ka-, the latter being closer to the actual Hebrew pronunciation. On the other hand, the spelling with Qua- would make perfect sense to someone whose first language is, say, Spanish or French.
The conclusion is that you must just choose the spelling that suits you best. Some decide more or less arbitrarily, perhaps going along with the one they encountered first in their studies. Others may find one spelling more logical than another. Others again may use techniques such as numerology to decide what form to use.
But, in the end, I think we have to accept that the only truly correct spelling is this one: קבלה