I currently own a Quad 909 and have for many years. I once bored some Cyrus smart powers and had them going in mono mode with my speakers and they didn't sound as powerful or as good as my 909.
However, I suspect the Cyrus mono amps are in a much higher class than the cheaper smart power amps.
Although the Quad is good, I have always found it slightly laid back, and suspect the Cyrus mono amps would outperform the Quad, anyone heard them?