Nooooooooo, stop using hacks!! If you want to separate something for IE use IE conditional comments. It really isn't the 'professional solution', it's outdated and very bad practice.
You're even showing a hack for the IE5 box model which IE6 doesn't use if you use a Strict doctype...which is all you should ever use unless you really are transitioning a website from one version of (X)HTML to another in which case a Transitional one is acceptable.
If you build websites well there's actually very few CSS changes you need for IE6. You also need to remember that trying to make websites pixel-perfect in every browser is not sensible.
You're even showing a hack for the IE5 box model which IE6 doesn't use if you use a Strict doctype...which is all you should ever use unless you really are transitioning a website from one version of (X)HTML to another in which case a Transitional one is acceptable.
If you build websites well there's actually very few CSS changes you need for IE6. You also need to remember that trying to make websites pixel-perfect in every browser is not sensible.