So far, I have not been pleased with any of my diy endeavors, including kits. The commercial stuff has always come out well ahead, even when I've used the same drivers. I learned that Dynaudio did not make their first line drivers available to do-it-yourselfer's; the versions that went to the aftermarket were factory seconds. I wonder if the same isn't true for other makers.
However, if the GR Research Criterion kit sounds as good as the demo's I auditioned, that changes everything. The Criterions are at the top of my list of one of the best monitors I've ever heard.