Economic alternative to pentax 55-300

Hi all,

Just after a few aideas please. I'm desperately trying to justify a K5 to the other half. Price is an issue here. So Although I know the 55-300 is a great lens, do you think there is a viable alternative (idealy with macro but not essential).

I like shooting birds and wildlife - I know 300mm is still tight, but it's probably good for me. So is there a decent sigma/tamron alternative that might save me money available.

many thanks all
Woody

--

After 10 years of picture taking - you'd have thought I'd have learnt to remove the lens cap...