www.smgf.org. I assume this is what you mean by Sorenson.
www.ysearch.org. He should establish an account there, so others find him.
www.dna.ancestry.com. He needs to enter his results there to search, unless he tested there. The tests are run by Sorenson Laboratories.
www.genetree.com. He also needs to enter his results, if he did not test there. Owned by Sorenson Laboratories.
www.genebase.org. You need to enter your results and send them a copy of the report.
Only if you do not find a close match within the surname, should you consider another surname. It is very difficult to find the common ancestor for different surnames, unless there is paper evidence. However, intersecting locales might lead you to evidence in court minutes or bastardy bonds.