bman, the EFI will be good for you if you just want a bit more thump. The megaphones are very loud, especially if unbaffled like the nfield one. I had a megaphone EMGO and it was loud till I baffled it heavily, then perhaps it was too quiet?! I only had it on a short spell before the EFI finally arrived from India.
I have the EFI on now but want it a bit louder. Its pretty quiet at low speeds, and has a nice sound when you're on it, but still a bit mild for me. The megaphone was WAY too loud. I've been trying EMGO exhausts and they are decent quality and really cheap (~$30). I bought a shorty emgo and I havent had a chance to put it on yet, but I'm hoping it will work out for me. Its open like a megaphone, but baffled and shaped like a EFI. I'm making a custom snuff r not for it so I can have quiet and loud when I want! Hopefully it works.