A Euro 6.9 will perhaps do 15 seconds in good hands. A US 6.3 in good hands can do 15.5 pretty easy. My best time in my own 6.3 was 15.07, and this was the record for an amateur in a US-spec 6.3 as far as I know.

A stock US 500E will do low-14 second quarter miles; a strong unmodified one will do 13.8-14.0 seconds. On nitrous, sub-13 second times are achieveable.

I have a video of Dan Smith in his 6.3 which is linked at:

http://www.nemonis.net/video/gvz3.avi

Cheers,
Gerry