I also would like to find a somewhat quiet aftermarket exhaust and fortunately live in a State that doesn't require emissions testing. You on the other hand have to pass emissions testing. I looked at the Remus Street Legal exhaust then checked the requirements for Japan. The cbr250r is actually 249.4cc and in Japan there are DB requirements but there are NO emissions requirements for anything under 250cc. I bet the remus is quiet but has no catalytic converter. I did find a stainless steel Akrapovic exhaust that is also street legal (a little bit longer and bigger in diameter than the others they offer) and comes with a mid pipe that flares to a larger opening where you can insert their optional catalytic converter. This one seems to be truly street legal for emissions and db levels. Problem is the Akro is expensive $425 muffler and mid pipe plus $88 for the cat (US dollars). I just can't quite justify the price because it looks good.
Quiet Aftermarket Exhausts?
I'm not thinking of buying one yet, but when that day comes, when I do need a new exhaust, over here, it's got to pass the MOT test. That means if it's got "Not for road use" stamped on it, and it's too loud, it isn't going to pass. I came across this website that is selling "EC" stamped exhausts, that are supposed to be road legal. I've heard many complaints on here about aftermarket exhausts being too loud. I quite like the look of the cheapest Remus can, and the cheapest Scorpion can (I think you can buy the Scorpion can in stainless steel elsewhere). I've also noticed that the Leo Vince Evo I and II is being sold on here as street legal. I wonder if they have quieter baffles in them than is sold elsewhere in the world, or they're bending the truth a bit. I thought this may be of interest to those of you who wanted a different exhaust, but also didn't want one that was unsociably loud. 
Exhausts for Honda CBR 250 R : Cheap : FREE UK DELIVERY : Motorcycle Accessories : RoarFactory.co.uk
Exhausts for Honda CBR 250 R : Cheap : FREE UK DELIVERY : Motorcycle Accessories : RoarFactory.co.uk
