I think you are off to a great start with the new camera. I didn't take any pics with mine until I'd had it for about 4 days. The quality of the images you should get are very high and can match, or closely rival a Canon 7d in quality terms. The sharp details you get in your images, mean you can do a lot of extra cropping and still keep getting great results, although obvioulsy, there's a limit. One thing I'm not seeing in your wren shots yet, is the finer details in the lower breast plumage (see my image below). Are you using Clear image Zoom (CIZ) by any chance? I find Smart Zoom (SZ) good, but CIZ smears details, although only noticeable when enlarged. My images have improved since I bought the camera last December, but I'm not sure why I suddenly started to get better with it. Practice, perhaps, I just don't know. I am constantly amazed at how good the quality is with this camera, but its not without its quirks. EG if you use SZ and go beyond 600mm the autofocus area switches to "wide" and the AF system reverts to the 25 point CDAF method. Generally that's ok for perching birds, but for birds in flight, it constantly loses them and is therefore hopeless. Enjoy the new toy and the associated learning curve.
Superb Blue Wren