@Spitfire omg.. that is the exact same thing I want to do with my black cbr250r.. But I'm having some troubles with getting the exhaust. & I like the WRX you have in the back tooI just installed the Yoshi slip-on. Its loud, but it has a deep throaty sound that I like. I got mine for $300 from a local bike shop (talked them into giving me a 25% discount since I bought my bike there). So I'm sure there has to be a place that would give you a similar price.
2011 Honda CBR250R Stock Exhaust Versus Yoshimura Slip-On Exhaust - YouTube