No idea on the layout, but I suspect you would have to get at least one before getting Quiet Casting and that's a pretty optimistic assumption. With a required skill of 50, I suspect it's a mid-low top tier perk.
Yeah that's what I was afraid of.. :/ The only way I would be able to make some room for that stuff is if I decided to get rid of my pick pocketing, stealth perks, and speech perks; frankly I don't really want to get rid of those. Guess I'll just have to rely on my dagger for stealth.