Mid-range zoom w/ best bokeh & least distortion?

Supposing you wanted a zoom that had at least 24mm on the wide end and at least 50mm on the long end, and supposing you were particularly interested in nice bokeh and minimum distortion, and supposing you couldn't afford the Nikon 28-70, what would you recommend?

By nice bokeh, I mean at least as good as the 18-70 DX and better than the 18-200 VR.

By minimum distortion, I mean less than the 18-70 DX.

Nikon, Tamron, Sigma, Tokina are all plausible contenders. I like sharpness but am not insane about it because of the size of prints I usually use, so sharpness is not my first criterion.

Mike