I recently upgraded the WiFi card in my 3,1 Mac Pro from the standard Apple Airport N Broadcom based two antenna card to an Atheros AR5BXB112 three antenna card. With the Broadcom card I was able to get 270Mbps link speed connecting to my 2013 AEBS 15 feet away. With the new card Im able to get 360Mbps (MCS index 21) fluctuating to 300Mbps (MCS index 15), but I was expecting 450Mbps given the close proximity. Even if I move the AEBS within a foot of the Mac Pro I still only get 360Mbps. Ive tried re-arranging the order of antenna connections on the card and even swapping in the supposed Bluetooth antenna (since there have been reports of this being mislabeled) but still cant exceed 360Mbps. Do I have a bad card or does this sound more like an antenna problem?