I bought a Darkglass Microtubes 500 v.2 and have been really happy with its sound when I play it with headphones or record it through my interface. The cab emulation is great and it growls very nicely. However, when I plug it into my 4x10 cab, the distortion is not there... It just sounds flat, even if I increase the Drive all the way to the top. The only way to get close to a good growly sound is to turn the volume up to about 50%, but then it's way too loud to play at home.

Is there any way to get the sound I hear in my headphones at low volume when playing through the cab?

I don't know if it matters at all, but the cab is 500W, 8 Ohms.