some bars I'd reccomend;
(excuse the spelling - I don't speak Flemish)
Den Engel in the Grote Markt - old style city pub.
There's a pub about a block behind Den Engle called In De Gloria which does amazing local food.
Paters Vatje(100 beers) just alongside the Cathedral north side.
Captain Zepo's - You'll have to ask where that is and there is a really nice little strange bar across the place from it.
De Bevern - near the waterfront it has a crazy mechanical organ in it. ask where it is - it's a bit of a mutant bar but well worth it for the organ and mutant locals!
And loads more - just wander about.
If you want to spoil yourselves, De Kline Zavel is probably the best restaurant I've ever eaten in. Not cheap by Antwerp standards but not so bad compared to what we're used to. You'd need to book.
enjoy - I wish I were going.