I wouldn't go the 70-300, as it's just a standard kit lens. the 120-300 is about 3x the price of the 120-400. I picked my 120-400 for 900, although i've seen it else where for $699. You can even look for a second hand one. I'd honestly just save for it man, it is totally worth it. I took it to the Racetrack on Sunday and I was amazed with it