I think you are asking which make better midi systems - i.e., all in one systems such as the one you have. When people on here refer to hifi, they are referring to separate systems - an amp, cd player, etc. etc.What is a better quality and sound between Panasonic vs Philips for hifi ?
You have stated you are very happy with your system, which plays music, however I doubt many would regard it as a hifi. It is a mini/midi all in one system. It's great you love it but it's not hifi.
As has been suggested above, if you'd like to hear what sounds good and better than what you have go and see a dealer.
All the best.