Originally posted by xs400 My second lens purchase was the Pentax DA 50-200mm. Very nice lens for the money. You can get one on ebay for about $150.
I used to have one (well, still do, but it collects dust on a shelf). It has been essentially replaced by a Tamron 70-300.
The DA 55-300 might be a better choice now, but it might not be. The IQ may be better (not much data so far, it's a very hard lens to find), but it doesn't have the close focus capability of the 70-300 (which I have used many times for flower shots), is far more expensive, and doesn't have the weight gain advantages one would expect for a DA lens over an FA. In fact, it's heavier than the Tamron.
My "super kit" (i.e. upgraded replacement for the kit) is a combo of a Sigma 17-70 and a Tamron 70-300. I love the combo. I have since added a Bigma (Sigma 50-500) to the crowd, but that is without a doubt a daylight-only lens.
Your next lens depends on your needs - If you like taking pictures of insects, a proper macro prime should be your next lens.
If you want to extend your flexibility in general, go for the Tamron 70-300 or the Pentax 55-300.
If you want to have a good all-around one-lens travel setup, get the Pentax or Tamron 18-250. (They are identical in design, the Pentax has better coatings but a worse warranty, they are about the same price.) I've assumed that any vacation I go on needs $450 budgeted for this lens.