[felix]

people here are comparatively wealthy

 

Haha  I think that is quite an understatement, especially after the recent abandonment of the franc's cap and its following appreciation. 

 

I'm curious to see your shots with the 300mm. I think a good quick test for centering quality would be taking a shot of some foliage at/near infinity. If both sides of the image appear equal in sharpness, you're probably fine.

 

What camera are you shooting with? If it's <24mp FX, you could try to close the 150-250mm gap with a manual 200mm lens. E.g. the Ai-S 4/200. It has a good reputation and it's relatively compact. You would, of course, have to change lenses even more often and I am not sure if the lens is good enough for a D800/D810 (most of my manual lenses aren't).