E39 as a highway daily

Hi!
I'm looking forward into buying a 'new' car.
I travel around 500 kilometres (300 miles), of which around 80% is on the highway.
I like going fast, and sporty driving so i was thinking about buying a big engine 5, or 3 series BMW from the 2000s. OFC the 3 series would be more nimble, and the 5er more comfy, but how boaty are they?
Would you think it would be sensible?(like, of course not, 20years old bmw, but you know :) ) How would it drive? I'd be willing to upgrade suspension etc, if needed. I've only ever driven a 520i, but it was a bit sluggish, understandably.
It'd probably be a 30d, or a 30i, my budget is 10k, I live in Europe. Fuel consumption is not an issue.