I've owned the ST-500, SX-500, and the Mini-MC5.
BRM's description is spot on. I'll also add, very dynamic, clean, with the lowest floor noise I've heard. Neutral, with no sound of their own. And the best bass control I've experienced.
From what I've heard, the 500's are the sweet spot of Wyred's line. The 1000's are for inefficient speakers.