Should I eliminate my preamp?

The theory is correct. Any preamp will add frequency response anomalies and distortion. You may prefer that sound to the unmodified signal, but it is good to be honest (as most of the posters in this thread have been) about what is actually going on. Sometimes I enjoy the listening to different DSP settings in my Yamaha A/V receiver  :-)

phomchick

Any preamp will add frequency response anomalies and distortion

Quite so. But with the best preamps, those levels are far below the threshold of audibility.

Any DAC or digital front end I've ever used as volume control simply,and I've owned some expensive ones,doesn't have the rich fullness of a top tier tube pre amp.

Although I've been rationally inclined towards simplifying a system as much as possible for the "purest" sound, personal experience has shown me that inserting a GOOD preamp between a source (w/volume control) and the amp often resulted in better sound. 
Since I listen to music instead of theory, measurements or specs, I keep the preamp in the system.

Any preamp will add frequency response anomalies and distortion. You may prefer that sound to the unmodified signal, but it is good to be honest (as most of the posters in this thread have been) about what is actually going on.

One of the most misunderstood tasks of any good preamp line section is to control the interconnect cable. This reduces coloration, which is often heard as an overall thinness and loss of bass impact.

Passive controls often have the issue of effectively raising the impedance of the source by putting a resistance in series with that source. This can often have the effect of acting as if a smaller coupling cap is used in that source, causing a loss of bass impact.

A buffer for the volume control (at the very least) is required; that buffer also has to control the interconnect cable, so in practice many preamps reduce the colorations described in several previous posts, with a much smaller coloration introduced by the line stage- a net improvement overall.