I'm running a Moon i5 into Totem Hawk speakers...the Totems are a great match for Sim since the two brands have a similar attributes (mainly the crystal clear highs, incredible soundstaging and fast, deep bass). In fact, with both companies being from Montreal, you'll see Totem speakers at the Sim facility and Sim equipment at the Totem facility. They really are made with each other in mind.
That being said, I heard the i5.3 on Dynaudio's and that was equally good...which makes sense since the Totem Hawks use Dynaudio drivers.
BTW, in case anyone's wondering, SimAudio is the real thing. The Moon i5 replaced a Bryston separates setup in my system and has been a huge upgrade. I hope one day to upgrade my CDP to a CD5.3!