All Zooms are a compromise, but the greater the ratio the greater the compromise as far as optics are concerned. I would stick with two lenses, but there's a lot to be said for just one to carry..

Your kit lens is an excellent kit lens. I'd keep it. That Tamron is not nearly as good optically. The Pentax is actually a Tamron so not so good either..

I've heard that the Sigma 70-300 is quite inexpensive and not too bad..

The Sigma 100-300 f4 is supposed to be very good, but a little on the expensive side...

Thanks alot. I was inclined to stick with the kit lens if for no other reason I have been very impressed with the quality and at a very reasonable price..

If your interested in landscape... you might check out the Sigma 10-20mm wide angle zoom. I don't have it but saw some very nice landscapes taken by Howard Goff a photographer from Great Britain. They were in the Feb 2008 edition of Digital Camera World. The link given washttp://www.360360.uk.com..

The photos were very nice and the website well done. I will look into the sigma lens. Thanks..

I'll second that Sigma 10-20. I love that lens. Originally I purchased the Tokina 12-24 but found it to be a pain always correcting in post. I bought the Sigma based on Thom Hogan's guide, and it's been a fantastic lens...

As others have said above - the more zoom range you cram into one lens, the more the compromises....

I have the Pentax 18-55 kit lens and added to it the Pentax DA 50-200, which is remarkably small and light: those two lenses together probably weigh about the same as the Tamron 18-250. A low-price alternative tele-zoom which is reckoned to be very good quality for the price is the Tamron Di 70-300 f/4-f/5.6. You can see reviews of these athttp://www.photozone.de.

Best wishesMike..

I'm following my own advice.... I have the Sigma 10-20 on order from B & H it's my first mail order I prefer having it in hand but no one locally has it. I'm a little nervous about the mail order bit but it's supposed to be delivered at my job tomorrow Hey it's even got me jacked to go to work on a Friday! I have a few locations in mind for this weekend provided we don't get the predicted downpour...