70-200F2.8 OR 80-400 f5.6

[Turn7]

For general use really. I shoot at Silverstone on occasion and struggle a bit for length and or speed.
Would be on a D300 and current long glass is Nikkor 70-300 AFS.

Obviously would use a convertor for lenght.

[Craikeybaby]

70-200 is too short for Silverstone, especially if you are in the public areas.

[Turn7]

Hence using a convertor...

[Mr.Tremlini]

2.8 can be useful in lower light, but personally I would go for the extra versatility of the 80-400 and turn up my ISO when need be.

[dogbucket]

Cameralabs have some comparison photos in their 80-400 review. 70-200 with teleconvertor is noticeably softer than the 80-400.

[missingman]

Buy a newer body, stick with the lens you have, crop the final image more.