for these speakers, ToFo. I have the 535, 545, and 555 amps in use. Best overall of these stablemates is the 100 watt rated 545. I think about 100 watt capability results in a low enough output z for good damping, and enough power for realistic dynamics. 60 watts is plenty, don't get me wrong. But 100 is NICE. The 200wpc 555 is running lately, with the preamp at about 5% from full CCW. But when you feel like rocking, crank the dial to 12 oclock for a spell...Samthe 5400 amp uses mosfets, right? a lot of people prefer them to the bipolars in mine.