~6.5 seconds is a pretty close estimate. The 6-speed might be marginally quicker (by a tenth) but the auto is no slouch, and the taller first gear means you get to wring it out a bit more.

I never went faster than 14.9 in the 1/4-mile with my old Limited... So, the Auto is pretty close to that, maybe ~2 tenths slower.

Here's a R&T Data Panel: