Personally I think the amount of acceptable drone is very different from person to person. It's very subjective.
I notice little to none with this setup. In all reality, it isn't that loud. I think the louder you go, the more drone you might hear. This is the sport version, so it's nowhere near as loud as the race. Also, with the stock cats and x-pipes, it's not very loud at all. At idle, it sounds pretty much like stock, but gets louder from there. Now if I got some catless x-pipes or HFC's, then the sound would be very different. That is probably my next step.
'11 BMW E92 ///M3 - ZCP and DCT
'13 Toyota Tundra - 4x4 Platinum CrewMax, 5.7l iForce V8