No bookshelf speaker is flat to 50 Hz, no matter what their specs say. On the other hand, they can be helped by room interactions, so it's really hard to say what's an acceptable rolloff point--and that leaves aside the most important question: What's acceptable to YOU?
I recommend that you try to borrow a pair of monitors and try them out in your room, preferably for a week or two, to let your ears get used to the new sound. That's the only way to know whether such a speaker will work for you in your room.
I recommend that you try to borrow a pair of monitors and try them out in your room, preferably for a week or two, to let your ears get used to the new sound. That's the only way to know whether such a speaker will work for you in your room.