I have a new Pentax K-5 and am currently using my lenses from my Pentax 35mm (35-80 f4 & 100-300 f4.5) which appear ok to me, however, I am new to this field and don't believe I am qualified to make judgement on this combination.
Has anyone tried this kind of setup and prepared to make comment on this combination?
Also, following much research and reading reviews and articles about many lenses, I am considering purchasing a Sigma 17-70f2.8 Macro. Am I heading in the right direction?
I would be most greatful for any feedback.

Regards,
Trevor