I experimented with the SQLUNDOPOLICY setting and with it set to NONE the CPU time did drop by 30 seconds but this setting generates warning messages for every Insert, Update, and Delete statement. That doesn't work for me and doesn't follow our programming guidelines of No Warning messages in the log. Plus, 30 seconds is still a full minute slower than the original Data step.
I then tried it set to Optional. This in a 9-10 second improvement so while faster it's not anywhere near the CPU speed of the Data step or a similar Proc Append (if that was an option in this situation).
I did crack open the Advanced Techniques and Efficiencies book as Cynthia suggested but haven't had a chance to go through the testing it suggests. Once I do I'll post what I find out.