i have an akra (not sure which one) and with a jet kit it sounds very good. it is not real loud but it has a deep "big bike" sound. in my opinion, it sounds better than most. it is much louder than stock..i have had several other riders say that they it soulds good at rpms.
The Sport stuff (street) uses SS headers. The Race is full Ti headers (about $1800-2400). The SS headers are a little heavier, and may be a little quieter. As far as the cans go, theres Carbon, Ti, and Full-Ti. The Ti uses SS end caps and internals, while the full-ti is all Titanium. I have had a couple of these (slip ons and full systems, guess which one came first???).
The Ak is relavively quiet, compared to many pipes, but creates a pretty distinct resonance that really comes alive at higher RPMs. On my R6 is makes it sound like an F1 car. Crazy raspy-howly. Performance is excellent for the low noise- very smooth, with a wide-open top end. Perfect in my mind....
The fit n' finish is perfect, and these things are super easy to install because they fit perfect every time (maybe better than stock!). Best pipe on the market as far as I'm concerned.