I have a Sony a6000 with an LA-EA2 adapter and Sony 75-300mm lens, and I would like to get a more powerful lens, but I don't have thousands of dollars to poor into a new lens. Any suggestions on a lens that won't bankrupt me (I'm assuming its probably not going to be an actual Sony lens). I've tried a 1.4x adapter and wasn't happy with it. How do you all feel about opteka lenses like this? http://www.amazon.com/Opteka-500-10...199955&sr=8-31&keywords=sony+emount+zoom+lens My assumption is that they are cheap because the quality is terrible. Is that a fair assessment? Thanks!