Anyone would help to understand output voltage gain graphics

I'm trying to make a simple cheap amplifier for my computer sound card and whatever I do I get more puzzled. I would like to make a "decent" amp and when I saw the gain vs frequency graphics I couldn't understand these big differences, could someone explain?

As you can see from the datasheet LM386 and LM384 seem very flat up to 10 kHz, I would qualify this as "good", but what happens with LM 1877? what does it mean a gain that falls linearly?

The puzzle goes on: TDA7265 seems to be beautifully flat at frequencies over 200 Hz, while TDA 2006 and TDA2030 are flat up to a point in the hundreds of Hz and then fall linearly, again in Gv instead of dB.

There is no reason to have gain above 20kHz. In fact, if the part retains gain at high frequencies, you will have to add external components to prevent it from oscillating.

You will not be wanting a circuit with a net gain over 20 dB (1:100; 10 mV in equals 1 volt out). You'll need to use feedback, which makes the amplifier as a whole largely unaffected by the gain of the amp chip itself. The exception is that LM386, I don't recall how those circuits work with such low gain. Look it up.

BTW, a configuration I did which created a good amount of power with low quiescent current and very low noise is a BUF634 inside the feedback loop of a TL082. Incredible headphone amp!

In Most cases there is also No Reason to Worry about the Frequency Response.
Most Speakers Won't Faithfully Reproduce below 100 hZ or above 15 Khz. Particularly those smaller ones for computers. And Room Acoustics also affects what you hear.

Additionally most speakers have distortion figures Exceeding 3% and Many over 10%.

An LM386 is Cheap, Simple, Relialable and probably about the best for your application.

Just My Opinion, Take care......Gary

Ideally, you would like to have a constant gain, no matter what the frequency of the signal is, be it 1 Hz or 1 GHz. But that is not achievable in pratice. So we have these "graphics" which we call the frequency response of the amplifier. The gain axis is in decibels. Every -3dB corresponds to a halving of gain.
The audible range of humans is about 20Hz to 20kHz. So a constant gain over this range would suit you fine.

LM386 is very flat up to over 10 kHz, it seems to me fine. TDA 7265 at audible frequencies is flat, it seems perfect, but what about TDA 2030 and TDA2006? at 10 kHz they have much less gain than a 1 kHz, does this mean they are anly suitable for low frequencies? and LM1877?

Decreasing 20dB from 1k 10 10k seems to me a huge change over the central audible frequencies while the datasheet recomends it for stereo phonographs, it seems clear it's not HIFI but I feel puzzled