I would add another passive to this list: The Sonic Euphoria autoformer, which I recently bought and enjoy. While I have not compared this directly to a true transformer preamp like Bent, a well-designed autoformer is said to preserve bass dynamics a bit better. In any case, many prefer the sound of a 'former passive preamp over a resistor-based one. You can see reviews of the SE unit at www.onsoundandmusic.com (current issue) and also www.6moons.com/audioreviews/eelectric/preamps.html.
[I have no affiliation with Sonic Euphoria.]
[I have no affiliation with Sonic Euphoria.]