The SRT-6 isn't as quiet. I have the minor wind noise issue around the window that i haven't gotten fixed yet, but the SRT-6 exhaust has slightly more bite and you can hear the engine and exhaust a "little" bit at those speeds, but there is almost no road noise. Still very pleasant. I like the low hum of the machine doing it's thing. Reminds me of the slumbering beast waiting to be unleashed under the hood...