ZX, your logic is a bit flawed here. Firstly, I kind of doubt that your speeds are still at 22/5. That may have been what you signed up for originally, but I'm pretty sure that's not what you have currently (speeds get bumped up all the time). If you want to PM me your cable modem's MAC address (the RF MAC) I can lookup which bootfile you have loaded onto your modem and see what speeds you're currently assigned.
Secondly, the number of channels bonded is based upon the settings in your modem's bootfile. So if you're subscribed to a service that only required 4 channels to bond then that's all you're going to get. Just because you get an SB6180 (which supports 8 channel bonding), doesn't mean it will bond 8 channels and give you extra speed. Where the 8 channel bonding will come into play is when you are subscribed to a service that
uses 8 channels, e.g., the 305/65 service when it is launched. For example when the 50Mb service was the top speed offered, even though the SB6120 modem supports 4 channel bonding only 3 channels were bonded at first. That has now been moved to 4 channel bonding, but it illustrates my point.
If you want to take a look at your modem status page, just go to
http://192.168.100.1 and your modem's status page will come up. On Moto modems it's under the "Signal" page.
Edit: Something else that might be affecting your numbers on performance tests that I discovered when D3 first launched and I was a tester for it, there are some anti-virus programs that screw with the way the numbers are interpreted. Some AV programs I tested would limit to 30Mb no matter what, and others had them spiking ridiculously high. Try disabling your AV and seeing if you get the same results.