Chair,
Of those places on the BBQ list, I really like Hog Heaven and Judge Bean's. Hog Heaven isn't a place you could take a client (unless he liked slumming it), even though the food is awesome. You'd literally be eating on a screened in porch, but it's the best BBQ in Nashville. Judge Bean's is someplace you could take a client, but it's just not quite as good.
Hog Heaven
Judge Bean's
Some other places I really like:
The Boundry
Excellent tapas, nice atmosphere, good place for a business-type dinner or a date.
Midtown Cafe
Seriously underrated on all these review sites, IMO. I've always loved this place.
Restaurant Zola
My favorite "nice" place in Nashville. I've been quite a few times, and it's never been anything short of excellent.
South Street
My favorite "casual" place. It's a treehouse, they've got great food (good pulled BBQ pork), and a fun atmosphere.
If I think of any others, I'll post them. I think you'd like any of these, though, and they all offer something a little different.