How many are using a camber kit with H&R's?
 

My alignment guy recommends I get a set for my front.
Thanks

If you are going 25.50" or lowerer, it's probably recommended.

using istook control arms w/ h&r streets

Same here.

what is a good height to run to avoid having to use a camber kit?

Wheels/tires/suspension/your S4 will all make a slight difference but I'd say 25.00" to be...
 

...conservative.

Currently, I'm at 24.50" on 18s and I'm OK. But if I drop another 0.5" I'll definitely need something.