So I have found I am using my 300 with a 1.4 or 2x tc more than with the bare lens, I would love the 400 if it was hand holdable like the 300 and I am not a fan of the 400 DO samples as compared to the 300 2.8 and 400 2.8 so I was thinking about the 500? Anyone end up in the same boat? How does the 300 2.8 is with compare to the 500's image quality, I realize it won't be as good, but how much worse? Since all the samples I have seen on here are downsized they looked very very good. Any real life advice is much appreciated.