Dinner for 8 in Barcelona
My best suggestion and one that can accommodate and does a good job with a business party of eight would be Restaurant Moo.
Attended a business dinner with 14 people and they had a nice set up. It was a set menu.
The food was good. The only thing I, personally, did not care for is the noise level it's high as the bar is adjacent to the restaurantseating area and it's hopping.
Good luck and enjoy our trip.