First question, how much insulation will be between your floor and your neighbor's ceiling (if it's none, which is probable the case, you asking for trouble, by putting in a subwoofer)? Second question, how loud to you like to listen to your music and at what time of day? Probably the biggest problem will the bass from your subwoofers bleeding into your neighbor's apartment, and it really doesn't matter whether the subwoofer is down-firing or forward-firing. And there is "no way" to stop this "sound bleed" unless you're willing to pull up your flooring and acoustically isolate and/or dampen the space between your floor and your neighbor's ceiling. If I was me living in such a situation, I would stick with stand-mounted monitors, and wait until I had a place where I could use a sub-woofer without bothering the neighbors. Other than that, once you get moved in, I would borrow a sub-woofer and test your system to see how much bass "sound bleed" goes into your downstair neighbor's apartment and what THEIR tolerance level might be. Remember if YOUR MUSIC is bleeding into their apartment, it's your responsibily to solve the problem.
PS: You signed the lease on the place, yet?
PS: You signed the lease on the place, yet?