frame stack and reach is only one part of the equation, a good starting point though. the L vitesse with a 10mm shorter stem would be the most obviously closest to your S6 with all else being equal.
all else includes...
- the number of spacers (adding spacers increases stack while slightly shortening the effective reach)
- stem length
- stem angle - a more sharply sloped stem is both lower in effective stack and slightly shorter in effective reach
- handlebar reach (there can be huge variations here, so unless two bikes use exactly the same handlebar then it needs calculating for - a Deda RHM has 75mm reach while a bontrager xxx aero is 93mm. 18mm, that's near twice the difference in reach between your S6 and the size L Vitesse)
allowing for all of that, adding 7mm of spacers to the M venon (above the spacer stack you use on the S6) would increase the stack to match your S6 while slightly shortening the reach. You could then plop the same stem and bar onto it and it should feel very similar...
it's all relatively small amounts of tweak between any of them, although a stem much shorter than 100mm on a bike that size is going to look silly and probably feel quite twitchy
Canyon quote Stack+ and reach+ numbers, these are in relation to the handlebar tops rather than the top of the headtube. Much more useful in the real world, although they still dont allow for bar reach.