A Boeing training pilot would be a good place, if you've got access to one (that's where I got my information). The Boeing Flight Crew Training Manual (737NG) says, for a stabilized approach, "the airplane should be at approach speed. Deviations of +10 knots to – 5 knots are acceptable if the airspeed is trending toward approach speed". Note that, coupled with Vref+5 approach speed, means that following standard procedure should keep you at or above Vref.
The speed portion of the FCTM also says, "When using the autothrottle, position command speed to VREF + 5 knots.
Sufficient wind and gust protection is available with the autothrottle connected because the autothrottle is designed to adjust thrust rapidly when the airspeed drops below command speed while reducing thrust slowly when the airspeed
exceeds command speed." That's basically a tacit admission that the autothrottle will hold you to at least VREF when you set commanded speed to VREF+5.
A different portion says, "When using the autothrottle, position command speed to VREF + 5 knots. Sufficient wind and gust protection is available with the autothrottle engaged that no further wind additives are needed."