Do I need to install a Sound-Card to enhance the sound quality (or music quality) over my Intel in-built sound card. Do I need to Sound card when I have Big Hi-Fi 5.1 channel Speakers (or above). For High Bass Music Should I upgrade my speakers or sound card ?
Just as inf.ig.sh wrote, you should upgrade speakers first.
This topic isn't as simple as it used to be before windows Vista and 7.
Back in DirectX 9 days, programs could via DirectX directly access sound card hardware and could use sound card's processor to generate real time special effects. This was mostly used in games, especailly together with Creative's sound cards. After DirectX 10, it is no longer possible to use sound card to directly process data. Instead, sound processing is done by the CPU.
Another way to directly access sound card is ASIO, but it is mostly used my musicians.
Since it is impossible for average computer user to easily use advanced capabilities of sound cards, the major factor now is quality of the signal output hardware.
A good sound card will prevent noise from network controllers an similar devices from affecting audio signals. Another point are available connectors.
Usually 5.1 systems are connected to computers in one of the following three ways: using 3 classic analogue stereo cables. One for front stereo, one for rear stereo and one for center and sub-woofer. This way is often only way on cheaper systems and is often found on more expensive for compatibility reasons.
The second way is using a single digital metallic cable. This way interference from the computer and other devices can be lowered. Also, the card connector does not need to be of high quality for low noise in the speakers because the electric signal which controls the speakers is actually made in the central speaker where the digital cable ends. This is often used by high quality speakers which will normally use high quality digital-to-analogue converters.
The third way is using digital optical cable. This way suffers from even lower interference because commonly found sources of electromagnetic radiation do not affect the light inside the cable. Just like in metallic cables central speakers has DACs which convert light signal to electric.
When purchasing sound card, you should take notice of available connectors. Cheap dedicated sound cards and a large number if integrated sound cards have 3.5mm TRS connectors. Some more expensive may have digital output using TRS connectors. Good cards will have miniTOSling or even full size TOSlink connectors for optical cables.
In this answer I have omitted details on professional sound cards used mainly by musicians. I do not know much about them, so I'd rather not make uneducated guesses.
You should upgrade the speakers. Upgrading the soundcard will improve the quality of the sound but the amount of bass will stay the same. Use a audio player with an equilizer is also a good idea.
If you already have good speakers, a better soundcard might help. For heavier bass, you may want to upgrade the sub-woofer of your stereo system.