You can get "shorty" downpipes that just replace the downpipe and not the midpipe. I think Bosal makes one.....
The highflow cat in the Helix downpipe is 8"-10" from the bellmouth, you could see it, but its not going to be right in front of you like the stockers.
Getting a catted downpipe will hurt your performance slightly, but you shouldn't be able to notice it. You might loose a few HP, but nothing major.
If I were to get a catted downpipe, I would go with a Helix. Great quality and easy on the pocket.