Your pre-amp is definately not the problem. I use a 380S with Watt/Puppy 8's and Pass Labs XA-100.5 amps. Your digital source is probably the problem. If you want a great balanced sounding system for digital for a resonable cost, PS Audio Perfect Wav Trans and DAC is the way to go ($6K). Very little listening fatigue...sounds smooth and detailed.
If you really want to hear the ultimate potential of your system, buy an analog front end (turntable).
If you really want to hear the ultimate potential of your system, buy an analog front end (turntable).