I run a 35w 6000k H7 kit in my A4 and spent time setting the lamps right, never been flashed or had any problem. Providing the lamps are projector and you keep with 4300k to 6000k you should find them loads better than the halogens.

Only issue I had was a ballast pack that failed earlier this year which cost me 12 quid. Not terrible in the 35k miles I've done since fitting.