Single-Ended vs. Push -Pull

You might want to look at the Quicksilver review in March, 2001 Stereophile, for the designer's comments on just this question. In "Manufacturer's Comments" in that issue, he also goes over the pros and cons of passive and active preamps. A balanced discussion, but I disagree with him, from personal experience, about having to have a high input impedance in your power amp(s) and also about having to use positively short interconnects. I've used a 10K ohm passive very successfully with Pass Aleph 3's used as monoblocks, input impedance 23K ohms (no higher), and the interconnects I used were 8' long, and unbalanced for LP play.

Larryr- My experience has indicated that SET sound is unique. There is a purity and harmonic structure to SET designs that I haven't heard in P-P. Obviously, it is much easier and efficient to make a high power P-P that can drive difficult load or relatively inefficient speakers. The usual differences are found in the weight and extension of the very low end and less compression under high spl levels. However, with the right speakers, good SET amps are a very special breed, capable of amazing dynamics and sonic realism especially in the critical midrange. Just my .02.