I am considering upgrading my equipment (lens) very soon. However, I am sort of torn. What do you guys suggest? Should I go for the 300 f4 with 1.4/2x converters, or for the 100-400? I have heard many good things about the 300, and obviously primes will give you better quality. I do plan on buying the 70-200 f2.8 in addition to these in the near future, so would it be smarter to go for the 300 now? Any advice is appreciated!