You would need to patch the EQ into a tape loop. Choose a set of record outputs from the AVR3300, send those into the EQ, and then send the EQ's line outputs into an unused input on the AVR3300 (don't use phono input). You will then use the receiver's rec/out select function to choose (when using the EQ) what you are listening to.
One possible downfall to this method is that you will be adding an entire new D/A-A/D conversion step to all of your sources, as the Denon will take the original source (digitizing if analog) and then convert to analog to send to the EQ, where it will re-enter the receiver only to be re-digitized. A better solution would be equalizing just before the power amp, but that would mean using external power amps....and hence negating some of the benefits of a receiver, that is to say cost and size issues.
Or, you could just skip using the EQ, and work on treating the room...