WOW, Thank you for your excellent advice.
a few more questions:
1. the 28mm is so rare and inexpensive, so I don't want to let go. I have not seen may go for sale here or on eBay, what do you say?
2. what do you say about sigma 70mm and 105mm compared to Pentax 70mm and 100mm? price and performance wise?
3. I also was thinking to buy this one
Sigma 70-300mm F4-5.6 DG OS Lens Reviews - Sigma Lenses - Pentax Lens Review Database to replace the 18-250?
The problem Is I cant use them all but want to keep them all, LBA problem from my part since I bought the K-5, three months ago.
Thank you.