I think most would suggest Theater Series four π speakers, as they are the most popular model for amps like the Zen. The Theater seven π is an excellent speaker too, but it requires corner placement. If you're on a budget, the tower two π's are great sounding speakers, as are the bookshelf version two π's. The one π is a good speaker too, but you would be best served using it with a subwoofer. The Thermionics are very nice and have a vintage sound, but they are very large. But any of these are speakers that I would recommend for the Zen.Last month, I heard a pair of Stage Series seven π's connected to a Zen Select amp. I wouldn't have expected the bass to be very good in this combination, but it sounded very, very good. You could hear the speaker's impedance influence in the circuit, but the overall result was very satisfying. I found most people were drawn to the room that had this system, and we all just seemed to sit there quietly listening, instead of socializing as is normal for these events. It just sounded very good.