I think I may have come to the realisation that the Nokia N91 SIP is for PoC only, not for VoIP.
I was reading through some of the docs on SIP for something entirely unrelated and realised that PTT (Push To Talk) has an ability called PoC (PTT over Cellular).
And it clicked, the SIP Settings in the Nokia N91 aren’t for VoIP in the sense I want, but purely for VoIP for PoC.
I’m going to look around for a PoC server and see if I can find one. (Maybe there is an Asterisk Module, w0000t)
I’m still stuck but I have posted a guide on how to get to where I am stuck 
I bought a Nokia N91 after I heard there was a built in SIP Client, as anyone who either knows me or reads this site knows I’m a technophile and sometimes an early adopter.
After a few hours of poking around the Internet and trying to set it up, I’m frustrated by being stuck at ‘– Got SIP response 415 “Unsupported Media Type” back from 192.168.14.205′. If I try to call it that is the message I get back from my asterisk logs.
The Nokia manual is useless, it has No Mention of the SIP Functionality that I can see, from what I read this was added in after the point anyway.
On a side note, I got my PDU webpage working with WiFi browsing on the mobile, It is even cooler than using my PDA to turn my Media stuff on and off (I hooked up my new lamp as well )
I’ll write up a Wiki entry on how to get to where I got with the SIP Client, as most of the guides I have read were etierh for the E60 (which is similar but not the same) or described no detail and no troubleshooting.
First off, I’m sorry about the lack of updates, as this was originally designed as my “Information Storage” and since I started up a Wiki, it has been less and less useful.
Adding on that I have also started a shared wiki at www.nervhq.com with Bir0, this might not get updated as often (I plan on concurrently updating both for the moment)