Using a SushiBox UA with the On/Off EQ section as my tube in. Soon to try a HW Slampegg Bee. Either pedal can be overdriven. Growl, like you said, is already available in the D-350.Play with the gain setting and the voice knob. You should be able to get it growly with quite a bit of attitude.
I miss the tube glassy sound, so I have a Sushi Box Westinghouse I'll put infront of mine; its a tube path with no eq (I don't want even more eq)
