There are the Indexers I currently use with Sonarr:
6box, NZB Tortuga, NZBGeek, NZBPlanet, Simply NZBs, DrunkenSlug & DOGnzb
I paid a fee for some of the above and just added DOG (trial) this morning.
Since I now use Sonarr & NZBGet exclusively, how do I know which Indexer is responsible for my downloads ? DOGnzb is a little costly and I'm not sure it really adds anything (for me).