logic7 definitely blows the stock system in my '08 out of the water (wife's car has logic7). But I've been very surprised with the quality of the base system. It's clearer than my H/K system was in my E46, with the same bass response and better midrange.
The difference between the base system and the enhanced/M/individual/whatever audio is the difference between a good stock system and one of the best systems offered on any car at any price. The base system doesn't compare well when you put it up against something like that.