The 353X is very neutral. The 727II is more powerful but not as linear. It has an 'interesting, tube-like' coloration, which might work quite well at lower listening levels. That also makes it quite bland. However, it becomes uncontrolled in the bass once the volume is pushed higher, and the highs can sound rolled off, albeit that also makes it somewhat less fatiguing with the SR-009. With a simple mod, the global feedback can be reinstated to sound more like a 'proper' solid-state amp. In that case it will sound much closer to the 323X with a bit of added power, although still slightly warmer. Some say the highs are a bit metallic and unrefined even after the mod, but with my current DAC, I haven't really heard that.