Losing the IS might suck, though. A used 70-200 f4 IS might not be too much more expensive and will be cover all bases, IMO. And you can always slap on a 1.4x third party TC and still get better images at 300mm@f/5.6 than the 70-300.
Also, the AF speed and noise of the 70-300 was a big bummer for me. I sold it to get the Tamron, which was far better.