I would stick to a high end air cooler until you decide to go custom water. Close loop coolers offer the same performance as high end air for more money and do not bridge the gap between Custom cooling and aftermarket coolers, so its not like a stepping stone.
What case do you have?
IMO closed loop coolers are much closer to air coolers than custom loops. If you plan to go custom, buying a cheaper cooler which is as good as these closed units is the way to go, so you can reach your custom loop budget all that much quicker!