2007 BMW 328i Upgrade vs New(er) Car

Hi all, first post here, but I could use some advice. I currently have a 2007 BMW 328i that has around 125k miles on it and is completely stock. With my budget of around $11k before taxes and the $6k I'd get for trading in my current ride (so $17k in total), I was looking at getting a used but newer (2012 or so) 328i or Audi A4 (would consider others though) which would probably have between 35 and 60k miles on it. However this got me thinking, for that $11k, would sinking some upgrades into my current vehicle be a better investment? This car needs to last me around 7 years more just so you know. So yeah, my question is: should I get a new(er) vehicle with around 35-60k miles on it without upgrades, or should I sink $11k into upgrades to make my current car better. Also, if the latter, what upgrades would you suggest? Thanks

2007 BMW 328i Upgrade vs New(er) Car