R4 Bandwidth

Does anyone have theoretical throughput figures for the R4 and for zigbee? I know that there is a module out there that "handles" this, but I am starting to think that the module is having adverse affects on the rest of my system performance.

As I write this, I am wondering if I should maybe offload the R4 Module to a separate processor??? This should stop the ungodly boot times that I started experiencing shortly after adding the R4s to the system (it's around 20-25 minutes and my queues and thresholds get demolished on boot).

Jeff