Antwerp is not very interesting imo, but the best belgian city to go to.
Lockwood is awesome for SB and diamond. The owner recently opened a shop that does more in steetwear called avenue (www.avenuestore.be), so that one gets some fresh shit.
And there's off course Lux streetfashion for jordans and air force 1's.
Definitely check out Avenue (www.avenuestore.be)
Fish and chips is good too, they have a nice selction of Cheap monday denim and some good deals to be had, there are also 2 comme des garcons stores as well as an A.P.C. shop somewhere.
CheckSuperfuture for adresses etc