Good replacement for kit lens ?

+1, even if it means waiting until you can find one in your price range. I paid just under £200 for mine on eBay nearly 2 years ago.

However, after several years of collecting lenses, I can vouch for the fact that the kit lens is really quite good and, particularly if your budget is tight, it's probably worth studying some samples from the 16-45/Tamron 17-50 to check that you will be happy with the improvements in IQ/functionality that you can expect.

It may be better, as others have suggested, to stick with your kit lens for a bit and save up for an ultrawide such as the Sigma 10-20, which will let you go really wide!

Good points of the Tamron:
- Excellent IQ
- A bit wider than the kit lens
- Still quite small and light
- Fast aperture (good for portraits/low light shooting)

Good points of the 16-45:
- Built better than the Tamron
- Slightly wider
- The deal you've been offered isn't a bad one and will save you trawling eBay.

Good points of the kit lens:
- You already have one
- It's pretty good, particularly in version 2 form (which I suspect yours is, if it was bundled with your K-x)