Originally Posted by lowfreq33
The output level on the direct out will be a little lower than ideal, but it will work. You'd be better off getting something like an ART Tube MP or a small mixer to boost the level after the direct out. Should be able to find either for around $50.
If the Rumble has a line level out, that might work going straight to the poweramp, depending on the input sensitivity of the poweramp (how strong a signal it wants coming in to work properly). Won't hurt to try. If it sounds weak/anemic, follow the above advice. Set the DI to post-eq if possible.