Wtf ... why quote my whole post for just two-three lines of text?!
Oh man.... you're thick.
No chip from the ones above would work best, because there are other chips that are more efficient and with less distortions. But considering you're a beginner, because the parts are easy to find, because it's easy to make the circuit even on a prototyping board, that's why I recommended you that TDA2040 or TDA2050. They're very easy for a beginner. So go with those.
I explained in that post exactly what transformer you'd need, or what power supply to use.
Some chips can work with low voltage, so they'll need current (amps) to output the audio watts they say they can do. ex TDA1519b mentioned only goes up to 18v but does about 12w (2x6w) with that.
Other chips are designed to work with higher voltage but can also work at some low voltage with reduced number of audio watts. The TDA2050 works as low as 10v and as much as 50v, but at 10v it only outputs 2-3 audio watts.
The transformer you show in pictures is for 9v... isn't it obvious from my previous comments that it won't be good since TDA2050 can only work from 10v ( or +/-5v, as in split power supply -5v, ground, +5v)
Next, I explained already that the amplifier needs an amount of watts to go in it, to output a number of audio watts.
Look at the damn plastic case the transformer came in, you will see it says something like 9v 300mA ... that's 9v 0.3 A ... the power would then be 9 * 0.3A = 2.7w. Even if the tda2050 could run at 9v, how many audio watts do you think it could output if you only give it 2.7 watts to play with and the chip is about 50% efficient with such low voltage? I went through all those explanations only to go over your head... damn.
That transformer in the pictures is very small, it's 300mA maximum. You can't do shit with it when it comes to audio amplifiers.
Look for something in the range of 18v (either with center tap or two 9v secondary windings) or a 24v transformer.
Popular values are 12v,15v,18v,20v,24v, 2x9 , 2x10, 2x12, 2x15, 2x18v, 2x20v, 2x24 (if they're separate windings you can use the windings in parallel to have 24v ac at twice the current). The tda2050 can work at up to 50v or +/- 25v so in split power supply you could use up to 2x18v and in single power supply you could use up to 24v AC or a transformer with 2x15v in series.
Look for a rating of at least 40VA. if it doesn't say an amount in VA, it should say amps ... 40 VA / 24v = 1.6A ... look for anything above 1.5A or 40VA.
Such transformer would be heavy, about 1 Kg, here's some examples of transformers that would work for two separate tda2050 (so you have stereo) :
http://goo.gl/MxAjM Look at the pictures to get an idea of size, look at details to see the weight, look at datasheet if you want... smallest (in voltage) selected there is with 2 12v secondaries which can be linked together to give you 24v AC rms, which when is converted to DC gets you about 32 V DC which is good enough for a lot of audio watts.
The cheapest there is even better with 2x15v dc, you could make even the split power supply version of the amplifier and it would give a lot of power.
Alternatively, you can get a 24v power supply, which may be cheaper:
http://www.ebay.com/itm/AC-220V-to-DC-24V-3A-72W-Switch-Power-Supply-Transformer-for-LED-Illuminated-/360525805977?pt=AU_B_I_Electrical_Test_Equipment&hash=item53f1033999http://www.ebay.com/itm/AC-220V-to-DC-24V-3A-72W-Switch-Power-Supply-Transformer-for-LED-Illuminated-/380532239639?pt=AU_B_I_Electrical_Test_Equipment&hash=item58997d2d179 volt transformer (i know nothing great ) but i think it has 1 primary and one secondary winding on it .
Of course it has one primary and one secondary, otherwise it wouldn't be a transformer, it would be a choke, or inductor.
Like I said, if it's only one secondary you can do the single power supply design, if you have two windings you have the option to do the split power supply or just connect the two windings in series to get one single big winding and do the single power supply design.