I run my pair of 485s with on older Hifonics Xi Olympus. It's a class A/B amp and it's super clean, something like .02%. It's a 4 channel bridged at 4 ohms and delivers 2x400 watts to the 485 pair. They sound incredible. That amp draws a good amount of power however.
If I were to do it again I would go with the class H Arc Audio KS-300.4 bridged. I think you would get 350 clean watts to each 485, and the power draw would be far less sine it's a H class amp.