I'm no expert, but one bit of info that may help is what tires and wheels are you running and what is the state of the suspension (any history of repairs or maint.?). These can make all the difference.

Also, 2007 was 11 years ago, so the level of expectations should be in that context, but I expect you're asking in that vein...

I also have a 07 4.8i and love it. It's not perfect and at it's age has all the problems+ that come with time but everything else is either too boring, over rated, or ugly. I can't provide any comparison to the 5 series, but I would suspect any truck type vehicle compared directly against it's sedan counterpart would not be as quiet.