Last time i was in froggys he had a new kakimoto system he might still have. Kakimoto's are far louder than Nur specs. I personally love the sound of a kakimoto for ten minutes but after a while it gets annoying, especially at 100-120kmph on a continuous rev the boom on motorway etc will wreck your head.
I have a 2.5" hayward and scott system i got from froggy and i reckon its the best compromise, a nice tone, but quiet enough not to melt your head. Plus its a more subtle looking tailpipe. Some of the bigger jap backboxes just look stupid, plus you'll be grounding it out on every speed bump and tear a hole in it within weeks.