Need a bench? Don't you mean want a bench? The only thing I've used a bench for in the last 4 years was to sit on between sets. Other than bench press, which does not make my shoulders happy, I can't think of much that a bench would be useful for in Crossfit. Bench press just doesn't come up that often, except when "Linda" comes up.
If I was going to get a bench, I'd go for a flat bench as they are simpler, cheaper, and probably last longer. The way I figure it, anytime you think about using an incline bench you should instead start thinking about doing the exercise standing on your feet.