yes, sha111, I agree with definityandcmuk, you should have at LEAST 4 CLANs in that switch, so that if you have a single failure, only %25 of your phones would need to re-register. Also, it will be difficult to do CLAN firmware upgrades, with so many phones depending on each of your 2 CLANs. CLANs are pretty inexpensive, at least compared to MEDPRO's. FYI, around 400 IP phones is the suggested maximum load, with 440 being the recomended max, you are way over this.
mitch
AVAYA Certified Specialist