Passive pre with class ''D'' power amps, issues ??

If I read the specs on it correctly the input impedance is high enough to work with most passives, but I'd be a little concerned about the gain (27db) and sensitivity (3V rms to full output). Typically something in the area of 1V would be ideal. However, this also depends on the source driving the passive. Most digital sources are 2V but some are higher. You could try a couple and see what happens.

I don't think a transformer based passive is going to make that much difference here given the gain and input sensitivity of the Bel Canto amp.

The high gain CIA D-200 or D-500 would be a much better candidate to match with a passive preamp. While I have experienced the benefits of transformer based passive designs, one non-transformer design recently caught my attention that I subsequently purchased and that is the Lightspeed attenuator. You can read up more on this uuit at DIYAudio.com. You can buy one pre-built by the original designer for about $350.

I believe he closed up shop.