I also have Gigaset C430H(s) with an N300IP.
I have recommended the Gigaset VoIP phones to several friends now and all are pleased with them. But features between various models seem to be very different which I find frustrating.
1) Not all have the INT button, so how would you call another handset in such cases?
2) You can set the default line to be either VoIP or POTS but how do you route the call out onto the other service [In my C47H I simply add a * after entering the number but that is not true for other handsets in the Gigaset range]?
3) When the phone is configured with addition VoIP services, how do you route the call out onto the preferred VoIP service?
4) How do you transfer a call to another handset?
If you have got the answer to any of these questions, please post your findings.