Suggestions For Enhancing The Factory Stereo In '08 Rx350

[Wimdermere]

My 2008 Rx 350 came with the factory basic stereo system(I was told it is a Pioneer). It sounds good but I would like to enhance the sound. I'm not looking for more base. This system provides plenty of that. I guess I'm looking for a more refined sound(similar to the Levinson stereo). Without changing the basic system what component would you recommend to add on. Any suggestions would be appreciated.