Hi David,
There is no other solution for work distribution since only a single virtual user can work with application's GUI at the same time. Having multiple users work with the GUI simultaneously would emulate several people fighting for mouse and keyboard (with unpredictable results). That is why only a single TestComplete/TestExecute test can be run on a machine at a time.
However, you can try to speed up your tests without distributing them to multiple machines. Try using suggestions provided in the following technical paper:
Automated Test Playback Performance Tips