Well, the first lens I bought after the kit was the DA 50-200 and I was very satisfied with it. For the price it will give you great bang-for-your-buck (in the under $200 range). I've since upgraded to the DA 55-300 (which is a bit more expensive) in order to get a bit more reach.
I can't speak for the sigma, or FAJ 75-300, but you might miss that hole between 55 and 70mm.
if you have the extra bling, the Pentax DA 55-300 is highly recommended.
better than the pentax or tamron or sigma 70-300 and the old 50-200 (which is very small). if you're on a strict budget, a tamron 70-300 can be had for around $100
The FA-J lenses are generally considered to be pretty poor quality. The DA 50-200 is a very good lens for $200. The Tamron and Sigma 70-300 lenses are both good too. I think the decision comes down to whether you feel you'll need the 200-300 range more than you'll need the 50-70 range and whether you're willing to carry around a significantly bigger/heavier lens to get it. Personally, I started with the 70-300 but disliked how bulky is was and switched to the 50-200 and have no complaints. Sure, sometimes 200 isn't long enough. but then, sometimes 300 wasn't long enough. And I can always crop.
I suggest reading in the reviews section, the FA J 75-300 was actually like pretty well, it's downside being rotating front element (like most budget zooms) and a very lightweight build. That said, they liked it overall very much and several prefered it over the Tamron.
I just picked one up off a member here last week after spending a lot of time researching it, but have not played with it much. I need to get the Pentax hood (was not included with the lens, shame on you Pentax, it's not exactly an indoor lens is it!) and a CPL. It will fill my need in October when I go to Laguna Seca, its much lighter then my old KA 70-210 tank lens.
Next year I plan on getting the DA55-300, but I've spent enough the past month on this camera, and $75 for this lens was a big win.
I've never spent more than 70eur on a zoom lens, but they're mostly manual focus stuff from the eighties. I'd look into used market for good old manual focus zooms, some of them are even better than the new auto focus lenses! Manual focus can be difficult but very rewarding
Is the Tamron 70-300 that much larger/heavier than the DA 55-200? I'm in the same boat as the original poster (photography novice, just picked up a k200d...) and I'll be traveling to Australia in a couple weeks and need a telephoto lense to complement the 18-55 II kit lens. Obivously lighter and smaller is better for my immediate needs, but I'm wondering if I'll miss the extra range of the larger lens.
well after looking thru reviews for the sigma, tamron and the DA 55-200 ive decided ill get the 55-200 due to the size and lens size.
Other than price, one of it's big plusses is that the front element does not rotate... thats pretty impotrant when you use a polarizer!
By the way, check out cameracanada.com (or their brick and mortar store "Forest City Image Center" on Dundas), the DA 50-200 is $169can there. It's $199 at Henrys.