First most folks seems to have issues with almost everyone of them altering the sound a little. I need one just to knock a little edge off, not much. All this being given which ones are going to stand the best chance of satisfying for the least amount of money?
Dr. Z Air brake does it for me. I use a rockcrusher to bring levels down lower for night time playing/practice. I find the Air Brake sounds more natural as well, although at it's most quiet setting(other than bedroom) is louder than the Rockcrusher's first level of attenuation. I run a 74 JMP SL and a Fuchs Train 45 both NMV amps.
Bonus with Rockcrusher is the line out with level control to send signal through effects for a W/D rig.