What you're trying to do is a compromise between having the output transistors turn off for low signals (not wanted), and high voltage swings in each output device, wanted. The ideal is to have the bias voltage as low as possible without the output devices turning off at all. For instance, a Class A amplifier is fully biased. In other words all the voltage is there to meet the needs of the largest signal all the time. When less than the maximum signal is there, the device dissipates the voltage as heat. Class B amplifiers turn off the output devices when no signal is present. Class A/B, which is what the vast majority of high-fi amps are, keep the output device with just enough voltage so that they don't fully turn off when a signal crosses zero to minimize crossover distortion. So less is better, but not too low. Also, some output devices aren't all that linear at really low bias, so getting above their non-linearity can improve the sound.
It should sound like it isn't there!
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