150i is fairly overpriced right now due to the new Gen6 Asetek pump (still think it's the only cooler with it) and the extra RGB factor. The maglev fans it comes with are EXTREMELY quiet and it is very good at noise-normalized performance but if you're looking for best temperatures, there are better 360mm or even 280mm radiators out there.
Thermaltake Riing Floe 360mm is better in terms of pure cooling, and EVGA CLC 280 is arguably some of the best cooling performance available to radiators with stock fans. If you want maximum performance, get the cheapest 360mm AIO and stick some EK Vardar or other high rpm static pressure fans on it.