09-06-10: GeorgelofiGreat point, George!
Plug your CD player or dac directly into your poweramp "this will be a perfect impedance match" As you have no volume control, first off play something that is low in level to gauge how loud it will be, doing this you are playing the "truest" form of cd/dac playback you can possibly get. Then slip the Lightspeed or any other pre active or passive back in adjust for the same level, and you will see and hear which one is "truest" to the source.
I actually did this years back with a borrowed Museatex Bidat when comparing my TVC to some active pre's I was considering. The Bidat(300ohms/3.5V RMS max) went directly to an Art Audio PX-25(180k/700mV/6wpc) SET amp driving Cain & Cain IM-Bens(~95dB/8ohm). Obviously, I preferred the passive route.
But, it did pose a problem playing vinyl w/ low output cartridges. I needed the extra gain of an active preamp or a phono pre with a lot more gain.