If you are using 2 maze$ blocks, and the RBX, you prolly should get the Iwaki. The RBX is rather pointless, as the gain you get from using it is minimal. Maybe 1 degree celsius difference from the TDX, but in order to use it you will need a bigger pump and more money. I would get the TDX, but that is up to you. And the three barbs on the TDX can be a little confusing for the watercooling n00b, but they come with a little bolt to plug one so you only have to use two.
Nothing against the Weaponcores, but you could custom mod your own for much cheaper. Hell, you can go to Danger den and get custom modded ones for very cheap. Granted, they dont look as sexy as the weaponcores, but they do the job for a fraction of the price.