The RBX (like the Whitewater) really like a high flow system....
may want a stronger pump for that... if you go with the maze 4 than that eheim is just fine... IMveryHO
Yes, the white-water and RBX work very well with high flow rates. They work better than other blocks at low flow rates also.
This is a common confusion. Look at this graph:
The whitewater is better starting at 1/4 gpm (really low flow) and gets even better with higher flow. Here is the whole review: http://www.overclockers.com/articles373/basum.asp