Just FYI...
Well, since I no longer needed to use the A4 in the previous network, I decided to replace the A2 with the A4 in my main setup. While I'm not really seeing any discernable speed variances, I can say that the error rate and dropped packets have dropped substantially. Both routers were configured exactly the same. I'll run the A4 for the next week and post any additional info I notice.
Dir-655 A2 1.30NA firmware
Dir-655 A4 1.30NA firmware