I think it's a bit unreasonable to say there's no "high tax rate" here. Yes, tax is complicated, but you can easily count on losing up to 50% of your salary in tax/social security if you're a higher earner. For example, DH earns €3500/month, but actually takes home just over €2000, plus meal vouchers. For his bonuses, he loses well over half. Out of a recent €2000 bonus, he saw €650! Yes, you get some tax back at the end of the year, but not that much unless you have kids in creche, garderie, a mortgage, a cleaner, etc.
I would count on at least €1500/month rent for a place in a decent part of Brussels, maybe a bit more if you plan to live close to the EU area or the international schools. If bills aren't included, you're looking at about €80/month for TV/internet/phone, plus electricity/gas/water on top. As a guide, we pay €100/month for electricity and slightly more for gas, plus about €400/year for water (family of 5 in a house).
If you have a car included in your package that's great, as car insurance is pretty expensive here (+/- €1500 a year for full cover, depending on age and car). And I think food's fairly expensive. We're a family of 5 and spend the best part of €750/month on our Carrefour shopping - and that's not really buying anything crazy.
I would say €2000 a month is a very conservative idea of a liveable salary, even with car, and school fees included....