In the search for a 'great' sound system there are many variables in it, including;
Personal music taste, sound isolation, clarity, bass, budget.
If you go into an electronics shop like Currys and listen to the headphones, you'll realise;
Cheaper headphones £80 and under- lack clarity, sound isolation and high notes but focus on mid-range and bass
Mid range headphones £140 and under- have moderate sound isolation, better clarity but still poor, no real bass but have a good mid-range.
Upper mid range £200 and below - tend to focus in bass, with good sound isolation, average clarity and a good mid -range.
High-end headphones £300+ - focus on clarity and sound isolation
Firstly the best way to improve your music system having good music! No I don't mean in taste, I mean in quality from the get go you want music to but as uncompressed as possible (higher the better), Cd's have a compression rate of 44.1 kHz, itunes mobile 128 kbps, Spotify variable through 3 settings Normal (96 kbps), High (160 kbps), and Extreme (320 kbps), I use spotify on extreme quality. So ditch the cd's and pirated music and get a good app!
(this site has music examples of differences
https://www.theverge.com/2017/4/5/15168340/lossless-audio-music-compression-test-spotify-hi-fi-tidal)
Now the actual car;
The mk5 standard set up is like the cheap headphones lacking in everything, now the best way to get a great sound system is to start with noise isolation, a number of us have put in sound deadening into our cars recently. Starting at the spare wheel well, by doing this you reduce interference to your music so you'll actually hear more of it, giving the impression of a better overall system especially with regards to clarity and bass.
Next you'll want to replace the speakers the standard system are paper when did you last say "damn that a4 book sounded great", paper is used because 99% of people don't know good music. Speakers are essentially comprised of magnets, suspension and diaphragms and basically these all add to the clarity of the sound that's emitted. You what a speaker that is strong to retain it's shape during use as it won't distort and will keep it's clarity. Mine are made from Magnesium Silicate Polymer with aluminium voice coils, with heavy strong magnets, so in summary heavy speakers are better most of the time (some cheap brands fake weight), this is the cost of speakers obviously just because they're expensive doesn't mean they're good, Alpine and Pioneer are very good systems are well respected for car audio.
Headunit and Amp - this is what powers the system you can't power your car with an AA so why supply your speakers with weak signals? The RNS 310, 510 and RCD510 head units are rated up to 300watt, so I stuck with one of these as well as they allow you to personalise your settings, bass, treble etc. But obviously if you run an aftermarket headunit and amp it'll be far better, a matching system is more likely to flow in my opinion as they're made to work together. That said many aftermarket automotive trimmers choose, herts and rainbow speakers, audison amps (all on the expensive end of the individual brands) and then pioneer headunit.
Hope that helps your decision.
