Hi again,
The title says it all really! I'm hankering for a better quality telephoto lens...don't get me wrong, I've had some great results with my Bigma, but it still falls pretty short in poor light, which sadly is a too regular occurance here in S Wales!

I'm unlikely to sell the Bigma as it's very versatile, but I'd like some sharper shots more regularly rather than just when the conditions are Bigma friendly!
I'm looking to get a half decent long prime, and was wondering what the best options for a Nikon user would be? I'd ideally not want to spend more than 2k, and even that might be stretching my budget a bit!
Is the 300mm f4 any good with a 1.4 or 1.7 TC?
Is the 500mm Sigma f4.5 any good (assuming I can get hold of one secondhand?)
Does anyone know of any other alternatives that don't require a second mortgage and would be a step up from the Bigma?
Thanks!