I just put in 2 GSP brand front CV axles. Like so many of you, I've learned the hard way that aftermarket axles rattle and vibrate like crazy. It makes the whole car feel old and shaky. I just called MWE to get 2 axles from them. The guy on the phone was very nice, and even took the time to explain to me a little of what he knows of the reason behind aftermarket axle vibration. Apparently, other manufacturers make CV joints that are too loose. This allows the differential to turn back and forth while the car is stopped, creating vibration and chatter while in drive or reverse.
It's obvious that MWE axles are strictly OEM rebuilds, since they won't even accept aftermarket axles as cores. He only works with genuine Subaru axles.
I'm going to try to get a refund on my GSP axles, since I haven't even driven 300 miles on them yet. They simply don't work.