410 hp might be a high goal for cam-only, though it has been done before. I think you should be looking more toward 370-380 rwhp, especially for an A4 car that is a daily driver; Streetability is different for everyone; it depends on what you can tolerate on a daily basis and how good your tune is; the tune gets the most out of the cam and the conditions you want the car to run as. With that said, I know a guy that runs an MS3 in his 2000 Firehawk, and I run the Torquer V.2 in my Z28; we both have ported LS* series heads (his are LS6 and mine are the 5.3L..) and we both get around 430-440 to the wheels with manual trannies. Don't forget to look at and update your valvetrain (springs, pushrods, blah blah blah) What is your intake manifold? The stock LS1 manifold?
If you want to get towards 410 rwhp on an A4 its going to take some more moola. You'd be better off getting it all done at once if you have the time and money; An intake manifold is a definite need to get that high, either an LS6 for a cam-only car or a Fast 90 or Fast 92 manifold for cam and heads. There is a good selection of heads, intake manifolds, and camshaft packages for sale through many of our sponsors; All in all, my head/cam swap ran upwards of $4500

but its a lot faster!