I believe an AP can handle around 15 7921 phones using the wireless A standard before voice quality problems becomes an issue.
If we put two AP with different channel using A near one another, are the 7921 phones capable of load balancing between the two AP's so they dont all join one access point?
We are using Cisco AP's, with 4400 controllers and WCS.
Of course they do. The APs transmit their load in their beacons. So the 7921s know which AP is more loaded than the other one. Also, the controllers try to load-balance even non-cisco wireless devices by denying (once) a device to connect to the AP that is very loaded. Then the client will (normally) try to connect to the second AP.