I have posted it earlier myself, but don't remember the link, so repost.
EDIT: I saw the project you found.
Don't like it very much: it uses the obsolete single supply configuration, has no short circuit protection, the feedbark network is unnecessarily complex (and probably wrong) and it's not easy to modify it into a mixed feedback system.
It is *very* crude, simplified to the maximum, but it works and can be built.
The PCB is easy to homebuild and works too.
And is very easy to modify to mixed feedback.
It's in Turkish but google can translate the page easily.http://translate.google.com/translate?sl=tr&tl=es&js=n&prev=_t&hl=en&ie=UTF-8&layout=2&eotf=1&u=http%3A%2F%2Fwww.diyaudiotr.com%2Fislecler%2Ftammetin.php%3Fmetinid%3D6%26durum%3De%23sonyorum
Some small corrections:
1) forget the 150W they claim and even 100W, it can provide honest and loud 70W into an 8 ohm speaker.
2) the supply voltage suggested is not too safe.
I suggest (by experience) not passing +/- 40V rails, which demand a transformer of no more than 30+30VAC (or 60VCT).
3) there is a separate .pdf with the ready to print PCB. www.diyaudiotr.com/resim/proje/kapibara/pcb.pdf
I recommend the iron on laser thermal transfer process, but it requires some experience.
Meaning, make 3 or 4 PCBs before trying this one.
I suggest not building this amplifier now, but it's good to know what you are getting into.
Start by making an LM386 amp.
Build and enjoy it. It is fun.
Later, build , say, some 15 to 30W with a TDA2003, TDA2030 or even TDA2050.
Build and enjoy.
Later, an LM3886 project. (50W)
Loud enough to play anywhere.
Go step by step, enjoy and learn along the way.
I see you live in Peru. Check what amplifier kits you can buy in an Electronics Shop.