Don,

Cats don't provide a lot of sound deadening - as evidenced by the rumble of my '93 Vette when did a cat-back system replacement with 2.5" pipes. I have set off car alarms pulling into a parking place. It's not cackly - just a nice hot-rod rumble. However, I don't get a second look from the police or at the safety check.

If you use cats with no muffler, you WILL attract attention.

Cat's aren't horribly restrictive, either. With your engine combination, I don't think you'll give up much if you put them in the system. However, mufflers are an absolute necessity.