Before diving into the download process, it is essential to understand why this OS is still sought after. El Capitan occupies a "sweet spot" in Apple's history. It is modern enough to run contemporary web browsers and productivity suites, yet old enough to support PowerPC applications via the "Rosetta" environment (though this was mostly phased out by this point, El Capitan is the last major version before the drastic file system changes introduced in macOS Sierra and High Sierra).
Furthermore, searching for “Extra Quality” in relation to OS downloads is a major red flag for malware, adware, or modified system files. No legitimate “extra quality” version of an operating system exists; the term is commonly used by piracy sites to attract clicks.
Once you have the official `Install OS X El Capitan