Akra, for 06-07 is not a true slip on, it is just replacement bolt on canisters, Leo makes a true slip on system that is from the cat back and includes both mufflers, as does KR Tuned, I am almost positve that Ti-force does as well, those would be about the only slip ons I would buy, a few other brands make a slip on but swith to one canister, which looks bad to me.
I've got the Leo's, but the install was a BITCH. The adapter from the cat to the first turn had to be pretty heavily "massaged" before it bolted up properly. The cans also require a little ingenuity, as they don't line up straight on their own. The straps can cause them to hang crooked.
After the install issues, though... BOOYEAH. They're great.