if money is the issue why not look at the tamron 150-600?
I mean thats why I picked it up as its a bargain and for my usage its perfect. ie just getting into supertele shooting
and birding.
If I were shooting long stuff all the time or professionally I would opt for the 200-400 though, eventually I can see myself stepping up to this lens but until that time I think the Tamron suits my limited needs perfectly for now.