You're going to get honest answers from people who prefer the sound each way.
The direct drive method, (no preamp) operates your system without any additional circuitry and connecting cables. There is certainly good argument for less is more in this case.
Ultimately, the answer comes down to equipment. The best quality preamp will sound better in most every situation. The best preamps will do a better job of driving the interconnect cable and input stages of the amps, while providing additional gain and dynamics.
The problem is, it may require a very high end preamp to overcome the direct drive method.
Personally, I prefer the sound with my Callisto in the system, even if I had no additional sources.
The direct drive method, (no preamp) operates your system without any additional circuitry and connecting cables. There is certainly good argument for less is more in this case.
Ultimately, the answer comes down to equipment. The best quality preamp will sound better in most every situation. The best preamps will do a better job of driving the interconnect cable and input stages of the amps, while providing additional gain and dynamics.
The problem is, it may require a very high end preamp to overcome the direct drive method.
Personally, I prefer the sound with my Callisto in the system, even if I had no additional sources.