This is probably more of a creative question than a language one, and tofro made some very nice suggestions.
To add something about your specific question, "Stärke" and "Kraft" can both mean "power", but they have different nuances. "Stärke" can also refer to "strength", "fortitude" and the like. It doesn't have to be physical power.
"Kraft" on the other hand typically focusses on physical strength. It can also have negative connotations like in "viel Kraft, wenig Hirn" (roughly translates to "muscles all over, but empty in the brain").
If you want to go with the German translation of "Power & Performance", I'd say it's a matter of what you want to emphasize - the sheer horse powers of the cars or their overall "strength".