Try the Benchmark LA4 if absolute transparency is one of your goals. Prior to owning a Benchmark stack, I was of the belief that distortion and noise performance is not so critical. Turns out that notion is very wrong. I figure the reason that some low THD+N products sound mediocre is because they still suffer from significant crossover and intermodulation distortion, and channel crosstalk.
Returning to tubes following a stint with the Benchmark gear reveals that those supposedly innocuous low-order harmonics are indeed a detriment, especially with respect to listening fatigue.