To start with, you using the free version - you can't use G729 at all, not even on the phones themselves. Change everything to g711 and start there. Check out http://myvoipspeed.visualware.com/ and see what you get for internet quality. Your specs are fine but if your line is bad then your calls will be bad. Choppy voice can come from several areas - bad routers, too much equipment in the way etc. What's your config?