t46g sound quality problem vs t20

[asinshesq]

I just checked the active codecs on my t46g and they appear in the following priority:
pcmu
pcma
g722
g729

I saw a list somewhere else that had the last two switched (g729 and then g722) so I tried that but no difference. If the only calls I am worried about are via a patton 4114 fxo gateway to a US pstn, what codec should I be listing first? Also, do these codecs have anything to do with how my plantronics headset communicates with the t46g? If so, how should I be setting things up to make sure the connection to the headset sounds good?

One other suggestion I saw was to change the jitter setting from adaptive to fixed at 120ms/120ms/120ms. Is that something that will help with drop outs?

Any other ideas?