Just keep in mind that the best spots have a veeeeeery long waiting list, so you should consider to act, at least, a few months before your scheduled occasion.
Also, in terms of budget, if you are not used to Brussels’ standards, you might find the average price to organize an event in Brussels completely insane.
However, this is how it is.
A low-cost solution may be to ask a local association or theatre: they may offer less conventional but more affordable event venues.
Or just ask Smart Videos: we have this bad habit to find solutions for event organizers.