Purchase an Ace a few weeks back to replace an older Krell integrated into Totem Forests (87db 8 ohm, 50-200 watts) that are reputed to be power hungry. Ace has no issues driving them. NYC apt so not playing ear bleed levels but they can easily get loud. Really easy to set up streaming and good, recent dac implementation.
Not familiar with details on S40 but wanted to share very favorable experience with Ace. Good luck. Dokosan