[Boromir88]

I did find the quote that Sauron ended up surpassing Morgoth in power. This is from HoME: Morgoth's Ring, Myths Transformed:

Sauron was 'greater' effectively, in the Second Age than Morgoth at the end of the First. Why? Because, though he was far smaller by natural stature, he had not yet fallen so low. Eventually he also squandered his power (of being) in the endeavor to gain control of others. But he was not obliged to expend so much of himself. To gain domination over Arda, Morgoth had let most of his being pass into the physical consitituents of the Earth--hence all things that were born on Earth and lived on and by it, beasts or plants or incarnate spirits, were liable to be 'stained'. Morgoth at the time of the War of the Jewels had become permanantly 'incarnate': for this reason he was afraid, and waged the war almost entirely by means and devices, or of subordinates and dominated creatures.
Sauron, however, inherited the 'corruption' of Arda, and only spent his (much more limited) power on the Rings; for it was the creatures of earth, in their minds and wills, that he desired to dominate. In this way, Sauron was also wiser than Melkor-Morgoth. Sauron was not a beginner of discord; and he probably knew more of the 'Music' than did Melkor, whose mind had always been filled with his own plans and devices, and gave little attention to other things. The time of Melkor's greatest power, therefore, was in the physical beginnings of the World; a vast demiurgic lust for power and the achievement of his own will and designs on a great scale.....