Hi Source,
What do you want to display? An LM3915 circuit per channel will display output power on 10 LEDs. Each LED shows double the power of the previous one. ;D
Whether you need a preamp depends on the level of your music source.
At an output per channel of 10W into 4 ohms, the output level is 6.3V. The bridged circuit has a voltage gain of 36dB, which is about 60. So the input level is about 105mV. You should allow extra gain for your volume control, so if the music source is about 330mV or less, then a preamp is recommended.
I don't think a TDA7350 will produce 22W. That is with a high supply voltage of 14.4V, at a very high 10% distortion, and only at 1kHz. With a 13.2V supply and at clipping, it will produce only about 10W.
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