I must not understand the trunk service and pbx. I do not understand what this may have to do with call quality.
There are many reasons to chose one SIP/pbx provider over another, most related to cost and QoS. Call quality is mainly dependent on latency, circuit quality/connection, and bandwidth/codec. "For me",
pbxes.org's call quality seems better than
sipsorcery's. I was also able to get calls connected on a more consistent basis than sipsorcery...YMMV. However you started your post stating that the solution was "buggy".
As for the other options, I am trying to go free, if it is possible 3G voip. I do not see the point of merging home lines and mobil. .
You'd be hard pressed to get "free" VoIP service, that allow calls to the PSTN, without use of an additional phone number/service/cost. But again,
Skype Out will let you make calls with your current "cell number" as the caller ID. "$3/mo for unlimited minutes" is a very inexpensive way to expand/leverage a cell service provider's cheapest plan. The reason "I" merge Vonage service with mobile (on one devices) is that Vonage not only provides unlimited calling to the US, but also unlimited "free" calling internationally (YNMV), of which my g/f calls her family everyday in Europe...along with the fact that my home number is the number I've had the longest, and provide to businesses. I also need/want a fax line.
The cost of Vonage on a monthly basis, is similar to adding "unlimited calling" to the cost of a mobile plan, however I have more features provided with Vonage (i.e. Ring Blast, availability numbers, etc). So I pay for the least expensive mobile plan, but have additional/unlimited minutes and functionality with SIP service. Vonage services (4) phones in my house, so I don't have to worry about dragging my cell phone all over the house, along with providing the connectivity I need for my Satellite provider's update process.
I can only be on 1 at a time and prefer to not be locked down to a location because of a phone. THe point is to be totally mobile and voip- anywhere.
How would having (2) phone numbers working on (1) mobile device "lock you down"? I can also forward my work calls to my Vonage number, so I do not have to "stay in the house" when I'm on call. Vonage number ringing on my cell, and not using any "minutes", alows me to be infinitely more mobile.