One of the reasons I thought I could get away with no preamp is because the Behringer has volume controls for each channel.
Yes, it sounded so bad that I switched out the monitors, then made sure I was using the same cables and everything was fine.
Also, the DAC has sounded great in another application.
Re computer program, I use Windows XP and I am not an expert, but the OS usually recognizes whatever I plug in and it works fine.
For playback, I am using lots of different things, but Foobar and WAV files whenever I am testing, and in this case to discover how bad it sounded.
Re "sending" 16 or 20 bits or whatever.....not sure how to change those settings, but I think in "preferences" in Foobar.
But I am not talking about splitting hairs - I am talking about really pretty bad, muffled, veiled, distorted sound compared to the same amp and the same speakers and the same cables in another desktop system.
Everything is the same, other than the fact that the good sounding desktop signal first goes through a Behringer DEQ2496 which functions as a preamp of sorts.
So I would guess either an "impedance mismatch" of some sort, or insufficient gain, but again, a bit puzzling and appreciate all suggestions.