Your speakers are of relatively low efficiency. That's the issue, not power or quality of power. As willemj pointed out, unless you level matched the Rotel and Yamaha for your comparison, it's likely the Rotel was playing at a higher volume when you perceived the improvement.
If you want low volume dynamics, you simply need speakers of high quality and greater efficiency.
If you want low volume dynamics, you simply need speakers of high quality and greater efficiency.