I would probably prefer a wifi module as opposed to the router, but haven't found one with an SMA connector that I can attach my amp to. If I don't find something I like, I have considered using one of my routers instead.
I assume you upgraded to the HMC6343 for the added tilt compensation. The one I was looking at has 3-4 degree accuracy instead of 2 degrees like yours. From your experience, do you think the extra accuracy makes a significant enough of a difference?
As for mounting my compass, I was considering the mast method to avoid motor noise, but I hadn't really thought about vibrational noise which the mast may well amplify. Also the mast may prove problematic depending on how I mount my pan assembly on top of the robot.