Any shortie headers will work with a normal length mid-pipe. So you'll be okay using the BBK shorties. As far as sound, the car will be a little throatier but not much because the stock cats are still restricting flow and volume.
Switching to any high flow catalytic convertor will increase power and sound. It's also hard to say if you will throw a check engine light too. This really depends on how free flowing the cats are. Sometimes they flow too well and the cat efficiency light goes off. If that's the case, you can always install MIL Eliminators
to take care of the check engine light.
Let me know if you have anymore questions!